{
"sidecar": "watches-glossary",
"codex": "watches",
"schema_version": "0.1",
"generated": "2026-09-26",
"policy": "No entry is published without a Tier 1 or Tier 2 source. Where no authoritative body defines a term in common trade use, the entry says so and states what was checked — an unanswered question is published as an unanswered question, never filled in from an uncitable source.",
"domains": [
{
"id": "standards",
"name": "Standards and certification"
},
{
"id": "mechanism",
"name": "How a watch works"
},
{
"id": "measurement",
"name": "Units and measurement"
},
{
"id": "trade",
"name": "Trade and law"
},
{
"id": "materials",
"name": "Materials"
}
],
"entries": [
{
"term": "Chronometer",
"slug": "chronometer",
"aliases": [
"COSC-certified",
"chronometer certification"
],
"domain": "standards",
"status": "verified",
"short": "A precision rating awarded to a watch or movement by a neutral testing body, not a type of watch and not a function.",
"full": [
"COSC, the Swiss body that issues the certification, states: \"A chronometer is a high-precision timekeeping instrument, set to operate with great precision under various conditions of use.\" It adds that a chronometer \"is certified by a neutral official body, such as the COSC in Switzerland, which carries out rigorous testing of the watch or movement and issues an official certification.\"",
"COSC's own published criteria: a testing period of 15 days, in five different positions and at three different temperatures (8°, 23° and 38°C), with an average daily rate that \"must be between -4 and +6 seconds per day\". COSC states it tests every watch submitted rather than sampling.",
"The underlying standard is ISO 3159:2009, Timekeeping instruments — Wrist-chronometers with spring balance oscillator, whose published scope states that it \"lays down the definition of the term 'chronometer', describing the categories, the test programme and the acceptable minimum requirements for wrist-chronometers\".",
"What this Codex does not do: quote ISO 3159's definition. The standard is paywalled and only its abstract is public, so the definitional clause itself has not been read. The −4/+6 figure is published as COSC's statement, cited to COSC, and not attributed to ISO."
],
"related": [
"chronograph",
"master-chronometer",
"poincon-de-geneve"
],
"sources": [
{
"tier": 1,
"citation": "COSC, \"COSC FAQ: All your questions answered\"",
"url": "https://www.cosc.swiss/cosc-faq",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "COSC, \"Chronometer Certified\"",
"url": "https://www.cosc.swiss/certified-chronometer",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 3159:2009, Timekeeping instruments — Wrist-chronometers with spring balance oscillator, edition 2, published December 2009",
"url": "https://www.iso.org/standard/54804.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Chronograph",
"slug": "chronograph",
"aliases": [
"stopwatch function"
],
"domain": "mechanism",
"status": "verified",
"short": "A watch that can record an elapsed interval: a function, not a precision rating. Constantly confused with chronometer.",
"full": [
"The Seiko Museum Ginza gives the etymology: \"Combining the Greek words 'chronos', meaning 'time', and 'graphos', meaning 'to write' or 'to record', the name chronograph literally means 'a device to record time'.\"",
"The distinction that matters. A chronograph is a function: the watch can start, stop and reset a measurement of elapsed time. A chronometer is a rating: a designation whose definition, test programme and minimum requirements are laid down in ISO 3159 and awarded after testing by a neutral body.",
"The two are independent. A chronograph may or may not be a chronometer; a chronometer may or may not be a chronograph. The museum notes the confusion itself: \"A similar word is 'chronometer', which refers to a device used to express time extremely accurately.\""
],
"related": [
"chronometer"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The Stopwatch and the Chronograph Part 1\"",
"url": "https://museum.seiko.co.jp/en/knowledge/story_06/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 3159:2009, Timekeeping instruments — Wrist-chronometers with spring balance oscillator",
"url": "https://www.iso.org/standard/54804.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Divers' watch",
"slug": "divers-watch",
"aliases": [
"diver's watch",
"dive watch",
"ISO 6425"
],
"domain": "standards",
"status": "verified",
"short": "A defined category under ISO 6425:2018, with requirements a watch must meet, not a style of watch.",
"full": [
"ISO 6425:2018, Horology — Divers' watches, states in its published scope that it \"specifies requirements and test methods for divers' watches and for saturation divers' watches for use in deep diving\".",
"The scope defines what the standard applies to, verbatim: \"It applies to divers' watches designed to withstand diving in water at depths of at least 100 m and equipped with a secured measuring system to indicate the diving time, which is visible in darkness.\" It adds that it \"indicates the marking which the manufacturer is authorized to apply to them\".",
"So a rotating bezel, a rubber strap or a depth marking do not by themselves make a watch a divers' watch in the standard's terms. The standard is separate from ISO 22810, which covers ordinary water-resistant watches.",
"Edition 4, published October 2018, confirmed as an International Standard in 2024."
],
"related": [
"water-resistant-watch"
],
"sources": [
{
"tier": 1,
"citation": "ISO 6425:2018, Horology — Divers' watches, edition 4, published October 2018, confirmed 2024",
"url": "https://www.iso.org/standard/66517.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Water-resistant watch",
"slug": "water-resistant-watch",
"aliases": [
"water resistance",
"ISO 22810",
"30m 50m 100m rating"
],
"domain": "standards",
"status": "verified-with-open-question",
"short": "Covered by ISO 22810:2010. What the depth marking means is less settled than the internet suggests, and this entry says exactly what is and is not documented.",
"full": [
"ISO 22810:2010, Horology — Water-resistant watches, states its scope in full: \"ISO 22810:2010 establishes the requirements and specifies the test methods used to verify the water resistance of watches. Moreover, it indicates the marking which the manufacturer is authorized to apply to them.\"",
"What the public scope does not say. It makes no reference to test pressure, to bar or metres, to usable or diving depth, or to any relationship between a marking and an activity. Three things only: requirements, test methods, and authorised marking.",
"The widely repeated claim, and why it is not here. It is very commonly asserted that a \"50 m\" marking describes a static laboratory test pressure rather than a depth at which the watch may be used. This Codex drafted that claim, could not confirm it in ISO's published material, and withdrew it. ISO's own news release on the standard in fact uses depth language: \"If a watch is said to be 'water resistant' to 30 meters (100 feet), this means that for all aquatic activities down to a depth of 30 meters, the watch case should not leak.\" That release is editorial text published by ISO, not normative standard text; it is reported here for what it is.",
"The claim may well be correct; the normative clause is paywalled and has not been read. Until it is, this Codex states the question rather than answering it. The withdrawal is logged publicly as correction corr-2026-09-25-001.",
"For diving, the separate standard is ISO 6425."
],
"related": [
"divers-watch"
],
"sources": [
{
"tier": 1,
"citation": "ISO 22810:2010, Horology — Water-resistant watches, edition 1, published August 2010",
"url": "https://www.iso.org/standard/45334.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO, \"ISO standard for water-resistant watches makes 'huge splash'\", news release, November 2010, editorial, not normative text",
"url": "https://www.iso.org/news/2010/11/Ref1367.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Master Chronometer",
"slug": "master-chronometer",
"aliases": [
"METAS certification",
"METAS"
],
"domain": "standards",
"status": "verified",
"short": "A Swiss federal certification of the finished, cased watch: distinct from chronometer certification, which is generally of the movement.",
"full": [
"The Federal Institute of Metrology METAS publishes what its watch certification covers: \"The accuracy of the chronometer under various influencing factors (temperatures, positions, magnetisation, used power reserve); the validation of the power reserve; the water resistance of the watches.\"",
"The rate requirement, as METAS words it, is that a watch \"must reach a rate accuracy of 0 to +5 seconds per day, i.e. it must never slow down and not be more than five seconds ahead of the actual time\".",
"METAS also certifies mechanical watches as \"resistant to magnetic fields of 1.5 T (15,000 G),\" a far higher field than the everyday exposure covered by ISO 764.",
"The governing document is METAS-N001, Requirements for the certification of movements and mechanical watches. Its contents are not quoted here: the document could not be retrieved, so no clause-level detail, test-day count or per-criterion limit is attributed to it."
],
"related": [
"chronometer",
"magnetic-resistance",
"power-reserve"
],
"sources": [
{
"tier": 1,
"citation": "Federal Institute of Metrology METAS, \"Watch certification\"",
"url": "https://www.metas.admin.ch/en/watch-certification",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Poinçon de Genève",
"slug": "poincon-de-geneve",
"aliases": [
"Geneva Seal",
"Geneva Hallmark"
],
"domain": "standards",
"status": "verified",
"short": "A state-backed Geneva hallmark for craftsmanship and durability, guaranteed by the State of Geneva and administered by TIMELAB.",
"full": [
"The Poinçon de Genève certifies, in its own words, \"all the qualities of craftsmanship to ensure regular and long-lasting operation,\" covering the craftsmanship, the regularity and durability of operation, and certificates of origin.",
"It rests on Geneva cantonal law I 1.25, passed by the Grand Council of Geneva in 1886 and updated in December 2008 as the law relating to the Geneva Laboratory of Horology and Microengineering.",
"Two bodies, not one. The State of Geneva is the legal guarantor; it delegates control and marking to TIMELAB, the Geneva Laboratory of Horology and Microengineering, which operates the Poinçon de Genève Office. Sources routinely collapse the two: the guarantee is the State's, the certification work is TIMELAB's.",
"It is a craftsmanship and origin mark, not a rate certification. TIMELAB separately runs the Observatoire Chronométrique+ for chronometer testing."
],
"related": [
"chronometer",
"master-chronometer"
],
"sources": [
{
"tier": 1,
"citation": "Poinçon de Genève (TIMELAB / Republic and Canton of Geneva), \"State guarantee\"",
"url": "https://www.poincondegeneve.ch/en/page/state-guarantee",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Poinçon de Genève, home page",
"url": "https://www.poincondegeneve.ch/en/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Magnetic resistance",
"slug": "magnetic-resistance",
"aliases": [
"antimagnetic",
"magnetic resistant watch",
"ISO 764"
],
"domain": "standards",
"status": "verified",
"short": "Covered by ISO 764:2020, which addresses everyday magnetic fields, not the high-field resistance some brands certify separately.",
"full": [
"ISO 764:2020, Horology — Magnetic resistant watches, states: \"This document specifies the minimum requirements and test methods for magnetic resistant watches. This document applies to magnetic resistant watches designed to withstand daily magnetic fields. Moreover, it indicates the marking which the manufacturer is authorized to apply to them.\"",
"The phrase \"daily magnetic fields\" is the boundary of the standard. High-field claims (METAS certifies resistance to 1.5 T, or 15,000 gauss) are a different and much more demanding thing, and are not what an ISO 764 marking indicates.",
"Edition 4, published February 2020, confirmed as an International Standard."
],
"related": [
"master-chronometer",
"gauss"
],
"sources": [
{
"tier": 1,
"citation": "ISO 764:2020, Horology — Magnetic resistant watches, edition 4, published February 2020",
"url": "https://www.iso.org/standard/70610.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Shock resistance",
"slug": "shock-resistance",
"aliases": [
"shock resistant",
"ISO 1413"
],
"domain": "standards",
"status": "verified",
"short": "ISO 1413:2016 defines it by a specific simulated fall: one metre onto a horizontal wooden floor.",
"full": [
"ISO 1413:2016, Horology — Shock-resistant wrist watches, states: \"ISO 1413:2016 specifies the minimum requirements for shock-resistant wrist watches and describes the corresponding test method. It is based on the simulation of the shock received by a wrist watch while falling from a height of 1 m onto a horizontal wooden floor.\"",
"One metre onto wood is the whole of it. A marking of shock resistance under this standard says nothing about heavier impacts.",
"Edition 3, published April 2016, confirmed 2021. The title changed between editions: the 1984 edition read \"Shock-resistant watches\"; the current one specifies wrist watches."
],
"related": [
"jewel"
],
"sources": [
{
"tier": 1,
"citation": "ISO 1413:2016, Horology — Shock-resistant wrist watches, edition 3, published April 2016, confirmed 2021",
"url": "https://www.iso.org/standard/62753.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Second",
"slug": "second",
"aliases": [
"SI second",
"definition of the second"
],
"domain": "measurement",
"status": "verified",
"short": "The SI base unit of time, defined since 2019 by fixing the caesium-133 hyperfine transition frequency.",
"full": [
"The BIPM's definition: \"The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s⁻¹.\"",
"Equivalently, as BIPM also puts it: \"The second is equal to the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the unperturbed ground state of the 133Cs atom.\"",
"Every accuracy claim any watch makes is ultimately a claim measured against this. Adopted by the 26th CGPM in 2018 and published in the SI Brochure, 9th edition, 2019."
],
"related": [
"quartz-movement",
"gauss"
],
"sources": [
{
"tier": 1,
"citation": "Bureau International des Poids et Mesures (BIPM), \"Second\", SI base units; definition adopted by the 26th CGPM (2018), SI Brochure 9th edition, 2019",
"url": "https://www.bipm.org/en/si-base-units/second",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2029-09-26",
"confidence": "high",
"autolink": false,
"autolink_note": "Too common a word to auto-link; linked by hand where the SI unit is meant."
},
{
"term": "Gauss",
"slug": "gauss",
"aliases": [
"G",
"magnetic flux density",
"15000 gauss"
],
"domain": "measurement",
"status": "verified",
"short": "A CGS unit of magnetic flux density, not an SI unit. 1 gauss = 10⁻⁴ tesla.",
"full": [
"Watch specifications state magnetic resistance in gauss rather than in the SI unit. Neither source cited here is a watch source, so no marketing figure is quoted in this entry; what follows is only what the metrology bodies publish about the unit itself.",
"The SI coherent derived unit of magnetic flux density is the tesla (T), listed in the SI Brochure as Wb/m², or kg·s⁻²·A⁻¹.",
"The gauss does not appear in the current SI Brochure at all, and is not among the non-SI units listed there for use with the SI. It is a CGS unit.",
"The conversion, from NIST: 1 gauss = 1 × 10⁻⁴ tesla. So 15,000 gauss is 1.5 T.",
"A wording caution. The current Brochure contains no blanket sentence forbidding units it does not list, so \"BIPM deprecates the gauss\" is not a supportable claim. What is supportable is that the gauss is not an SI unit and is not listed among the non-SI units for use with the SI."
],
"related": [
"magnetic-resistance",
"second"
],
"sources": [
{
"tier": 1,
"citation": "BIPM, The International System of Units (SI), 9th edition, 2019, Table 4 (coherent derived units) and Table 8 (non-SI units)",
"url": "https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B.9",
"url": "https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-27",
"review_due": "2029-09-26",
"confidence": "high"
},
{
"term": "Power reserve",
"slug": "power-reserve",
"aliases": [
"autonomy",
"running time"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "In universal trade use, and defined by no standards or metrology body that publishes publicly. This entry records what was checked.",
"full": [
"Every brand quotes a power reserve. No authority publicly defines it.",
"What was checked. The published catalogue of ISO/TC 114, the technical committee for horology, contains no standard on power reserve, autonomy or running time. ISO does standardise autonomy for battery-powered watches (ISO 12819:2009, on evaluating the battery life of a battery-powered watch), which makes the absence of a mainspring equivalent more conspicuous, not less. BIPM does not define it; it is not a metrological quantity. METAS tests it, listing \"the validation of the power reserve\" among its certification criteria, without defining the term.",
"The one gap that remains. ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, published February 2026, \"defines the principal terms used in horology\". Its term list is paywalled and could not be read, so it may contain an entry. That single document would settle the question.",
"Why this entry exists at all. A glossary that silently omits the terms it could not source is indistinguishable from one that never looked. The honest position is that in common use a power reserve is the period a fully wound watch will run unaided, that this usage is universal, and that no public authority has fixed its meaning or its method of measurement."
],
"related": [
"mainspring",
"master-chronometer"
],
"sources": [
{
"tier": 1,
"citation": "ISO/TC 114 Horology, published standards catalogue",
"url": "https://www.iso.org/committee/51734/x/catalogue/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published February 2026 — term list not public",
"url": "https://www.iso.org/standard/88512.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federal Institute of Metrology METAS, \"Watch certification\", uses the term without defining it",
"url": "https://www.metas.admin.ch/en/watch-certification",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Escapement",
"slug": "escapement",
"aliases": [
"escape wheel",
"pallet fork"
],
"domain": "mechanism",
"status": "verified",
"short": "The mechanism that lets the gear train advance in fixed steps while keeping the regulator oscillating. It is what makes a watch tick.",
"full": [
"The Seiko Museum Ginza's definition: \"An escapement is a device that rotates a wheel in fixed intervals while continually applying intermittent force to maintain the oscillation of the regulator.\"",
"Two jobs in one mechanism: it releases the gear train a step at a time, and it feeds a small push back to the oscillator to keep it going.",
"Why it is needed at all, in Grand Seiko's words: \"If the force from the mainspring were transmitted directly to the hands, they would rotate at an uncontrollable speed, making accurate timekeeping impossible… the escapement regulates the rotation of the gears to ensure precise timekeeping.\"",
"The audible tick of a mechanical watch is the escapement releasing and locking."
],
"related": [
"balance-wheel",
"mainspring",
"gear-train",
"jewel"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"First-ever mechanical clock\", Knowledge — Mechanical Timepieces 01",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces01/",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Grand Seiko, \"Mechanical\", manufacturer technical documentation",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Balance wheel",
"slug": "balance-wheel",
"aliases": [
"balance",
"hairspring",
"balance spring"
],
"domain": "mechanism",
"status": "verified",
"short": "The oscillating wheel and spring that set the rate of a mechanical watch: the portable answer to the pendulum.",
"full": [
"The Seiko Museum Ginza: \"The balance wheel is a mechanism that, while possessing the same isochronous quality as the pendulum, is not so susceptible to vibrations and is therefore portable.\" That portability is why wristwatches exist.",
"Its construction, per the same source: \"a fine 'hairspring' fitted into a metal wheel, with one end of the spring fixed to the wheel and the other fixed to the body of the timepiece.\"",
"Isochronism is the property that makes it work: \"The hairspring is isochronous, so the cycle remains unchanged even when the oscillation angle shifts.\" The swing can vary in size without the period changing much, which is what lets a watch keep time as its mainspring runs down.",
"Grand Seiko on the balance's place in the system: \"This regular oscillation is transferred to the pallet fork, which controls the rotation of the escape wheel at a constant rate… The hairspring is the critical component at the heart of a mechanical watch as it governs its precision.\""
],
"related": [
"escapement",
"mainspring",
"gear-train"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The invention of the balance wheel and the cylinder escapement\"",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces04/",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Grand Seiko, \"Mechanical\", manufacturer technical documentation",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Mainspring",
"slug": "mainspring",
"aliases": [
"spring barrel"
],
"domain": "mechanism",
"status": "verified",
"short": "The wound spring that powers a mechanical watch. It replaced the hanging weight and made portable timekeeping possible.",
"full": [
"The Seiko Museum Ginza on why it mattered: \"The invention that replaced weights as a driving force was the mainspring. Compared to a weight, a mainspring was much smaller and not so easily affected by movement or tilting of the clock.\" A weight-driven clock must hang still; a spring-driven one can be carried.",
"How its energy reaches the hands, per Grand Seiko: \"A wound-up mainspring exerts force to turn gears at a set speed as it unwinds… the mainspring unwinds gradually and evenly over a long period of time, and this consistent motion is transmitted through the gear train.\"",
"In an automatic watch the mainspring is wound by the wearer's motion turning a rotor, and by the crown. Neither page cited here states that in those words, so nothing is quoted for it; the automatic and rotor entries carry the sourced account.",
"Not stated here: the barrel that houses the mainspring. No Tier 1 or Tier 2 source reachable for this entry describes it, so it is not described."
],
"related": [
"escapement",
"automatic",
"power-reserve",
"gear-train"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Portable Clocks\", Knowledge — Mechanical Timepieces 02",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces02/",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Grand Seiko, \"Mechanical\", and Caliber 9R01 instruction documentation",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-27",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Gear train",
"slug": "gear-train",
"aliases": [
"wheel train",
"going train"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "The set of wheels carrying power from the mainspring to the escapement and the hands.",
"full": [
"Grand Seiko: \"the mainspring unwinds gradually and evenly over a long period of time, and this consistent motion is transmitted through the gear train to drive the hour, minute, and seconds hands with precision.\"",
"The train does two things at once: it carries the power along, and it steps the speed down so that one wheel turns once a minute and another once an hour.",
"On the term \"going train\". The traditional name for the timekeeping train specifically, as distinct from a striking or chiming train. The only definition located for it sits in a glossary compiled by an auction house, which is a source type this Codex does not cite. It is recorded here as a synonym in trade use, without a definition, pending a citable one."
],
"related": [
"mainspring",
"escapement",
"jewel"
],
"sources": [
{
"tier": 2,
"citation": "Grand Seiko, \"Mechanical\", manufacturer technical documentation",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2028-09-26",
"confidence": "medium"
},
{
"term": "Jewel",
"slug": "jewel",
"aliases": [
"jewels",
"17 jewels",
"ruby",
"cap stone"
],
"domain": "mechanism",
"status": "verified",
"short": "Synthetic hard stones used as bearings at points of wear. The number on a dial is a construction fact, not a quality score.",
"full": [
"The Seiko Museum Ginza on why they are there: \"The areas with which the shafts are in contact are required to withstand wear so as not to reduce their accuracies or fail.\"",
"What they are: \"A synthetic ruby, sapphire, or other hard stone are used, which are durable enough to have a high friction resistance.\" The word to notice is synthetic: these are manufactured stones, chosen for hardness. The page makes no statement about their value.",
"Where they sit: around the shafts as hole stones, with cap stones above and below on the escape wheel and balance, and at the pallet forks and impulse pin \"which wear easily\".",
"On jewel counts. The museum states: \"more stones are required in higher-class and more complicated mechanical watches although minimum 17 stones are good enough for functionality. For example, Grand Seiko High Beat uses 37 stones.\" Note that the page ties the count to two things at once: how complicated a movement is, and what class it is, so it does not support reading the number as a measure of one alone. ISO 1112 governs how the count may be marked and advertised."
],
"related": [
"escapement",
"balance-wheel",
"gear-train"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Why are Stones Required in Watches?\", Knowledge — Trivia",
"url": "https://museum.seiko.co.jp/en/knowledge/trivia05/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-27",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Automatic",
"slug": "automatic",
"aliases": [
"self-winding",
"rotor",
"perpetual rotor"
],
"domain": "mechanism",
"status": "verified",
"short": "A mechanical watch wound by the motion of the wearer's arm through a pivoting weight.",
"full": [
"Rolex describes the principle in its own technology: \"In a constant state of unstable equilibrium, the half-moon oscillating weight is beholden to Earth's gravity… it rotates with the wearer's every gesture, and sways in one direction or the other.\" That motion is captured: \"The energy generated by these oscillations is transferred to the mainspring, which is continually wound, through an innovative system comprised of reversing wheels and a gear train.\"",
"Winding in both directions. A rotor swings either way, but a mainspring winds one way, so the mechanism must convert both directions into one. The Seiko Museum describes its own solution, the Magic Lever: \"regardless of the rotational direction of the rotor, the two pullets of the Magic Lever always generate a unidirectional movement and also make the transmission wheel always rotate in one direction\".",
"An automatic is still a mechanical watch. Nothing is electrical; the wearer replaces the daily winding."
],
"related": [
"mainspring",
"power-reserve",
"gear-train"
],
"sources": [
{
"tier": 2,
"citation": "Rolex, \"Perpetual Rotor\", Movements — Watchmaking Features; manufacturer documentation of its own technology",
"url": "https://www.rolex.com/en-us/watchmaking/features/movements/perpetual-rotor",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The Big Role of the Tiny Magic Lever\"",
"url": "https://museum.seiko.co.jp/en/knowledge/trivia04/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Quartz movement",
"slug": "quartz-movement",
"aliases": [
"quartz",
"32768 Hz",
"quartz oscillator"
],
"domain": "mechanism",
"status": "verified",
"short": "Timekeeping by counting the vibrations of a quartz crystal, almost always at 32,768 Hz.",
"full": [
"NIST states the general principle first: \"Clocks work by counting a periodic event with a known frequency.\"",
"Then the quartz case: \"With a quartz clock (like most wristwatches), a piece of quartz crystal is cut and used in an electronic circuit where it vibrates at a certain frequency (usually 32,768 Hz).\" And the counting: \"The frequency is 'counted' by dividing it by 32,768 to equal one second 'ticks'.\" NIST adds the reason this design is good: \"By dividing a high frequency down to a low frequency, the accuracy can be increased.\"",
"Why 32,768 Hz. Writing in the British Horological Institute's Horological Journal, NIST's Michael Lombardi records: \"The quartz watch industry standardised on 32 kHz crystals in the early 1970s due to their reliability, their compatibility with existing electronic circuits, their small dimensions, and their low power consumption.\" The value is 2¹⁵ Hz.",
"What is not claimed here. It is often said the figure was chosen because 2¹⁵ divides neatly through fifteen binary stages. That may be so; neither source says it, so this Codex does not.",
"The first commercial quartz wristwatch ran slower: the Seiko Museum records that the 1969 Quartz Astron used an 8,192 Hz oscillator, and \"a frequency of 32,768 Hz became the standard for later quartz timepieces\"."
],
"related": [
"second",
"escapement",
"balance-wheel"
],
"sources": [
{
"tier": 1,
"citation": "NIST Time and Frequency Division, \"Timekeeping and clocks FAQs\"",
"url": "https://www.nist.gov/pml/time-and-frequency-division/timekeeping-and-clocks-faqs",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Michael A. Lombardi (NIST), \"The Accuracy and Stability of Quartz Watches\", Horological Journal (British Horological Institute), February 2008",
"url": "https://tf.nist.gov/general/pdf/2276.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The birth of the quartz timepiece\"",
"url": "https://museum.seiko.co.jp/en/knowledge/Quartz01/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2028-09-26",
"confidence": "high"
},
{
"term": "Ligne",
"slug": "ligne",
"aliases": [
"lignes",
"l."
],
"domain": "measurement",
"status": "no-citable-value",
"short": "The traditional unit of movement diameter. Its metric value is quoted everywhere and could not be confirmed on a citable source.",
"full": [
"Movement sizes are still given in lignes: Seiko's 1913 Laurel is described by its own museum as having a 12-ligne movement. The unit descends from the French pouce, or Paris inch, of the pre-metric system, a ligne being one twelfth of one.",
"The problem. A metric value for the ligne is quoted on a great many websites, usually as 2.255, 2.256 or 2.2558 mm. Every one of those sources is of a kind this Codex does not cite: encyclopedias, dealer pages, enthusiast editorial and conversion charts. The only compiled glossary located that states a value is hosted by a horological association but was written by an auction house, which the source policy also excludes.",
"So no figure is published here. Three different values circulate at three-decimal precision; adopting one on the strength of uncitable sources would be exactly the failure this Codex exists to avoid.",
"How it gets resolved. The pouce derives from the pied du roi, which is documented in metrology history. A national metrology body or a university-press history of metrication would let the value be derived and stated properly. Until then the entry stands as a question."
],
"related": [
"second"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Japan's First Wristwatch, Laurel\", records a \"12 ligne movement\", establishing the unit's use without defining it",
"url": "https://museum.seiko.co.jp/en/collections/watch_previousterm/collect004/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Complication",
"slug": "complication",
"aliases": [
"complications",
"grand complication"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "Universally used, defined by no authority this Codex can cite. What was checked is recorded.",
"full": [
"A complication is, in ordinary trade use, any function a watch performs beyond telling the time. The word is everywhere. A citable definition is not.",
"What was checked and came back empty: The Seiko Museum Ginza's knowledge base, the Musée international d'horlogerie, the Science Museum Group including the Clockmakers' Museum, Royal Museums Greenwich, the Deutsches Uhrenmuseum, the Smithsonian, and the public pages of the British Horological Institute and the Antiquarian Horological Society. The term is also absent as a headword from the horological glossary hosted by the NAWCC.",
"What exists but is not usable here. Individual manufacturers publish their own operational tests of what counts as a complication, and the Fondation de la Haute Horlogerie publishes an entry. Neither route can carry a general definition on this Codex: a manufacturer is a Tier 1 source for its own technology, and \"complication\" is a general term of art rather than any one company's; the Fondation is an industry foundation and is not on the approved source list. No manufacturer's wording is quoted here, because none is cited on this entry.",
"Why museums explain mechanisms well and vocabulary badly. A museum's job is objects. Terminology is the province of standards bodies and horological institutes, and horology's vocabulary standard, ISO 6426-2:2026, is paywalled. That is the likely route to a citable definition, along with BHI and AHS print material."
],
"related": [
"chronograph",
"power-reserve"
],
"sources": [
{
"tier": 1,
"citation": "ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, published February 2026 — term list not public; identified as the likely route to a citable definition",
"url": "https://www.iso.org/standard/88512.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-27",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Hertz",
"slug": "hertz",
"aliases": [
"Hz"
],
"domain": "measurement",
"status": "verified",
"short": "The SI unit of frequency, equal to one cycle per second, used for the beat rate of a balance and for a quartz crystal's oscillation.",
"full": [
"The hertz is one of the SI units with a special name. BIPM's SI Brochure lists it in its table of coherent derived units as \"frequency hertz (d) Hz s−1\" (that is, one per second) and attaches footnote (d): \"The hertz shall only be used for periodic phenomena and the becquerel shall only be used for stochastic processes in activity referred to a radionuclide.\" The unit therefore counts repetitions of something that repeats regularly, which is exactly what an oscillator in a watch does.",
"The hertz also sits inside the definition of the second itself. The same brochure states: \"The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, ∆νCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz\".",
"In watches the figures are small or very large depending on the oscillator. For quartz, the Seiko Museum records that the 1969 Quartz Astron used \"a quartz oscillator with a vibration frequency of 8,192 Hz\" and that \"a frequency of 32,768 Hz became the standard for later quartz timepieces\". For mechanical movements the hertz is used too (European patent application EP 2 802 944 A1, filed by LVMH Swiss Manufactures, refers in its background to a \"4Hz oscillator\"), while vibrations per hour is also used in the trade for a mechanical beat rate, a unit the SI Brochure does not list."
],
"related": [
"vibrations-per-hour",
"quartz-movement",
"balance-wheel",
"second"
],
"sources": [
{
"tier": 1,
"citation": "Bureau international des poids et mesures (BIPM), The International System of Units (SI), 9th edition (2019), English text",
"url": "https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The birth of the quartz timepiece\"",
"url": "https://museum.seiko.co.jp/en/knowledge/Quartz01/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European patent application EP 2 802 944 A1, \"Watch movement comprising a tourbillon for a chronograph\", applicant LVMH Swiss Manufactures SA, published 19 November 2014 (text consulted via Google Patents)",
"url": "https://patents.google.com/patent/EP2802944A1/en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Vibrations per hour",
"slug": "vibrations-per-hour",
"aliases": [
"vph",
"alternances",
"semi-oscillations"
],
"domain": "measurement",
"status": "no-authoritative-definition",
"short": "The trade's unit for a mechanical beat rate: half-swings of the balance in an hour, counted two to each complete oscillation.",
"full": [
"A mechanical watch's beat rate is usually published as a number of vibrations per hour (18,000, 21,600, 28,800, 36,000) rather than in hertz. A vibration is a half-swing: the balance travelling one way and unlocking the escapement once. Two vibrations make one complete oscillation, so a figure in vibrations per hour is 7,200 times the figure in hertz. No metrology institute, standards body or museum consulted for this entry defines the unit or states that conversion, and BIPM's SI Brochure does not list vibrations per hour among the non-SI units it tabulates.",
"The Swiss industry does standardise the subject. The Federation of the Swiss Watch Industry FH publishes a list of available NIHS standards, valid from April 2026, which includes \"NIHSG_30-10_fr: Frequences - Appareils horaires a balancier-spiral\" (1968, modified 2022): frequencies for balance-and-spring timekeepers. The list gives titles only, so that document's definitional clauses have not been read here, and no standard in the list is titled for the unit itself.",
"What can be shown is how primary documents use the count. US patent 3,465,515, granted to Girard-Perregaux in 1969, describes \"the balance wheel to oscillate 18,000 times per hour whereby the escape wheel is freed and advances one-half its tooth pitch, five times per second\": 18,000 an hour and five a second being the same count, each event one unlocking. EP 2 802 944 A1 (LVMH Swiss Manufactures, 2014) speaks of \"a first number of alternations per hour, for example 21'600 vibrations per hour or 28,800 vibrations per hour\", treating alternations and vibrations as one thing.",
"What this Codex does not do: attribute the factor of two to an authority. Dividing those trade figures by 7,200 gives 2.5, 3 and 4 Hz, which is this Codex's own arithmetic from two vibrations to the cycle rather than a conversion any source cited here states. It is recorded here as trade usage, not as a defined unit."
],
"related": [
"hertz",
"balance-wheel",
"escapement",
"daily-rate"
],
"sources": [
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Liste des normes disponibles valable des avril 2026\" (list of available NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "United States patent US 3,465,515, \"High-frequency watch movement\", inventor Francis Jaquet, assignee Girard-Perregaux et Cie. S.A., filed 31 October 1966, granted 9 September 1969 (text consulted via Google Patents)",
"url": "https://patents.google.com/patent/US3465515A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European patent application EP 2 802 944 A1, \"Watch movement comprising a tourbillon for a chronograph\", applicant LVMH Swiss Manufactures SA, published 19 November 2014 (text consulted via Google Patents)",
"url": "https://patents.google.com/patent/EP2802944A1/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Bureau international des poids et mesures (BIPM), The International System of Units (SI), 9th edition (2019), English text",
"url": "https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Daily rate",
"slug": "daily-rate",
"aliases": [
"seconds per day"
],
"domain": "measurement",
"status": "verified-with-open-question",
"short": "How many seconds a watch gains or loses in twenty-four hours, written with a sign, as in the range minus 4 to plus 6 seconds per day.",
"full": [
"Daily rate is the quantity a chronometry test reports. COSC, the Swiss body that certifies chronometers, gives as the first of its criteria: \"Average Daily Rate: The watch must maintain an average daily rate between -4 and +6 seconds per day.\" It adds that \"the average daily rate must be between -4 and +6 seconds per day over the first 10 days of testing\". The sign carries the meaning: a negative figure is a watch losing time, a positive figure one gaining it.",
"A single rate figure is only part of a test. COSC states that \"During this time, the watch is tested in five different positions and at three different temperatures (8°, 23°, and 38°C)\" across fifteen days, and its published list of seven criteria also includes mean variation in rates, greatest variation in rates, difference between rates in horizontal and vertical positions, variation in rate depending on temperature, and rate resumption. Quartz watches are assessed under a separate procedure; FH's list of available NIHS standards names \"NIHS_93-16_fr: Horlogerie - Procedure d'evaluation de la precision des montres a quartz\" (2003, modified 2018).",
"What this Codex does not do: quote a standard's definition of rate. The underlying standard is ISO 3159:2009, Timekeeping instruments - Wrist-chronometers with spring balance oscillator, edition 2, published December 2009, whose public abstract says it \"lays down the definition of the term 'chronometer', describing the categories, the test programme and the acceptable minimum requirements for wrist-chronometers\". The standard is paywalled and only that abstract is public, so how it defines and computes rate has not been read here. The minus 4 to plus 6 figure is published as COSC's own statement and is cited to COSC."
],
"related": [
"chronometer",
"master-chronometer",
"hertz",
"amplitude"
],
"sources": [
{
"tier": 1,
"citation": "COSC (Controle officiel suisse des chronometres), \"COSC FAQ: All your questions answered\"",
"url": "https://www.cosc.swiss/cosc-faq",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 3159:2009, Timekeeping instruments - Wrist-chronometers with spring balance oscillator, edition 2, published December 2009, status Published",
"url": "https://www.iso.org/standard/54804.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Liste des normes disponibles valable des avril 2026\" (list of available NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium",
"autolink": false,
"autolink_note": "\"Rate\" is too common a word in ordinary English to link on sight elsewhere on the site."
},
{
"term": "Amplitude",
"slug": "amplitude",
"aliases": [
"balance amplitude"
],
"domain": "measurement",
"status": "verified-with-open-question",
"short": "The angular swing of a balance wheel away from its rest position, measured in degrees.",
"full": [
"The clearest definition found for this entry is in a granted patent rather than a standard. European patent EP 2 917 787 B1, held by Patek Philippe SA Geneve and published on 19 August 2020, speaks of \"l'amplitude d'oscillation du balancier exprimee en degres par rapport a la position d'equilibre\": the amplitude of oscillation of the balance, expressed in degrees with respect to the equilibrium position. The same patent compares a movement's behaviour at \"amplitude d'oscillation de 150°\" and at \"amplitude d'oscillation de 300°\", and records that \"la marche diminue progressivement au fur et a mesure que l'amplitude d'oscillation diminue\": the rate falls progressively as the amplitude falls.",
"Amplitude is read because it changes, and because a change in it shows up as a change in rate. French patent publication FR 2 767 205 A1, an optical and acoustic method of measuring balance amplitude filed in 1997 by Femto, states that an amplitude that is too small or too strong \"may, in fact, affect the accuracy of the watch when it is in a vertical position\", while fluctuations in amplitude over time may show \"defects in the gear train or the spring barrel\". The quantity is therefore used as a diagnostic alongside daily rate, not instead of it.",
"What is open: no standards body's definition of amplitude has been read. FH's list of available NIHS standards, valid from April 2026, includes one on horological vocabulary (\"NIHS_02-03_fr: Vocabulaire horloger - Partie 1: Definitions technico-scientifiques\", 1982), but the list gives titles and years only, not the text of the norms, and no standard in it is titled for amplitude. The definition above is quoted from a manufacturer's granted patent, a primary document, but not a normative definition issued by a standards body or metrology institute."
],
"related": [
"balance-wheel",
"isochronism",
"lift-angle",
"hairspring"
],
"sources": [
{
"tier": 1,
"citation": "European patent EP 2 917 787 B1, \"Mouvement d'horlogerie a balancier-spiral\", proprietor Patek Philippe SA Geneve, published 19 August 2020 (text consulted via Google Patents)",
"url": "https://patents.google.com/patent/EP2917787B1/fr",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "French patent publication FR 2 767 205 A1, \"Measuring balance wheel amplitude on mechanical watch\", applicant Femto, filed 7 August 1997, published 12 February 1999 (text consulted via Google Patents)",
"url": "https://patents.google.com/patent/FR2767205A1/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Liste des normes disponibles valable des avril 2026\" (list of available NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Isochronism",
"slug": "isochronism",
"aliases": [
"isochronous",
"isochronal"
],
"domain": "measurement",
"status": "verified",
"short": "The property of an oscillator whose period does not change when the size of its swing changes.",
"full": [
"Isochronism names an independence. European patent EP 3 206 091 B1, \"Resonateur isochrone d'horlogerie\", held by ETA SA Manufacture Horlogere Suisse and published on 23 January 2019, puts the mechanical condition plainly: \"Le couple est proportionnel a l'angle α dont la masse 5 correspondante pivote. La frequence est donc independante de l'amplitude de l'oscillation.\" Where the restoring torque is proportional to the angle turned, the frequency is independent of the amplitude of the oscillation. A watch whose balance is isochronous keeps the same rate whether it is swinging widely or narrowly, which matters because amplitude falls as the mainspring runs down.",
"The Seiko Museum, a museum source rather than a standards body, sets out the history: Galileo discovered the \"isochronism of the pendulum\", that the \"period of a pendulum's swing was independent from the amplitude of the swing\"; Christiaan Huygens then \"developed the concept of a highly accurate, isochronic pendulum by drawing a cycloid curve unimpeded by air resistance\", having \"demonstrated theoretically that a large-amplitude swing was subject to large error that precluded isochronism\". The museum adds that a spiral balance spring \"oscillates isochronously like a pendulum but is free from the influence of gravity,\" which is what carried the idea from clocks into watches. The Science Museum Group's record for a Thomas Tompion balance-spring watch of 1675-1679 states that when \"Christiaan Huygens (1629-1693) applied the spiral spring to the balance of a watch in 1675 it brought about an improvement in timekeeping comparable to that produced by the application of the pendulum to the clock\".",
"What this Codex does not do: quote Huygens. He set the work out in Horologium Oscillatorium of 1673, and a full page scan of the Latin text is downloadable from the Internet Archive, but it has not been read here, so no translation is offered as his wording."
],
"related": [
"hairspring",
"balance-wheel",
"amplitude",
"tourbillon"
],
"sources": [
{
"tier": 1,
"citation": "European patent EP 3 206 091 B1, \"Resonateur isochrone d'horlogerie\", proprietor ETA SA Manufacture Horlogere Suisse, published 23 January 2019 (text consulted via Google Patents)",
"url": "https://patents.google.com/patent/EP3206091B1/fr",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Christiaan Huygens (1629-1695)\"",
"url": "https://museum.seiko.co.jp/en/knowledge/inventors_01/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Science Museum Group Collection, \"Early balance spring watch by Thomas Tompion\", object 1985-1537, dated 1675-1679",
"url": "https://collection.sciencemuseumgroup.org.uk/objects/co33/early-balance-spring-watch-by-thomas-tompion-pocket-watch",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Christiaan Huygens, Horologium Oscillatorium, 1673 (Latin); full page scan, Internet Archive catalogue record",
"url": "https://archive.org/details/horologium-oscillatorium",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Tesla",
"slug": "tesla",
"aliases": [
"T"
],
"domain": "measurement",
"status": "verified",
"short": "The SI unit of magnetic flux density; one tesla equals 10,000 gauss, the older unit watch specifications still use.",
"full": [
"The tesla is an SI derived unit with a special name. BIPM's SI Brochure lists it as \"magnetic flux density tesla T kg s−2 A−1\", so one tesla is one kilogram per second squared per ampere, equivalently one weber per square metre. It measures the density of magnetic flux: the strength of the field a watch is actually standing in.",
"The unit watch specifications use is the older one. NIST's Guide for the Use of the International System of Units, Special Publication 811, gives the conversion in Appendix B.9 as \"gauss (Gs, G) tesla (T) 1.0 E-04\": one gauss is 1 × 10⁻⁴ tesla, so one tesla is 10,000 gauss. The gauss belongs to the CGS system and is not an SI unit, which is why a figure quoted in gauss has to be divided by 10,000 to be expressed in the SI.",
"Anti-magnetic claims on watches are almost always stated in gauss rather than tesla. The Swiss industry has a standard for magnetic-resistant watches: FH's list of available NIHS standards names \"NIHS_90-10_fr: Horlogerie - Montres resistantes au magnetisme\" (1965, modified 2020), but the list gives only the title, not the text of the norm, and no source read for this entry explains why the trade kept the gauss. The persistence of the gauss is recorded here as trade convention; the conversion above is given so that either figure can be turned into the other."
],
"related": [
"gauss",
"magnetic-resistance",
"silicon-hairspring"
],
"sources": [
{
"tier": 1,
"citation": "Bureau international des poids et mesures (BIPM), The International System of Units (SI), 9th edition (2019), English text",
"url": "https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B.9, \"Factors for units listed by kind of quantity or field of science\"",
"url": "https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Liste des normes disponibles valable des avril 2026\" (list of available NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Bar (pressure)",
"slug": "bar",
"aliases": [],
"domain": "measurement",
"status": "verified-with-open-question",
"short": "A non-SI unit of pressure equal to 0.1 megapascal, and the unit most often stamped on a watch's water-resistance marking.",
"full": [
"BIPM's SI Brochure lists the bar in its Table 8 of non-SI units, with the value \"1 bar = 0.1 MPa = 10⁵ Pa\": one bar is a tenth of a megapascal, or 100,000 pascals. Its footnote records that \"The bar and its symbol were included in Resolution 7 of the 9th CGPM in 1948.\" The brochure explains why such units are tabulated at all: \"It is recognized that some non-SI units are widely used and that this is expected to continue for many years. It is therefore important to recall the values of these non-SI units in terms of SI units, because the SI is the internationally agreed reference with respect to which all other units are defined.\"",
"The bar is tolerated rather than adopted. Announcing an update to the brochure on 4 June 2026, BIPM stated that the revision makes explicit that \"non-SI units do not hold any special status within the SI\", and reorganised the listed non-SI units into four categories.",
"On a watch the number appears on the caseback. Seiko's own customer-service page shows markings of 3BAR, 5BAR, 10BAR, 15BAR and 20BAR, and warns that \"a watch's water resistance is not permanently guaranteed\". The figure comes from a laboratory test: ISO 22810:2010, Horology - Water-resistant watches, edition 1, published August 2010, \"establishes the requirements and specifies the test methods used to verify the water resistance of watches. Moreover, it indicates the marking which the manufacturer is authorized to apply to them.\"",
"What this Codex does not do: state what pressure or duration that test applies, or what a given marking permits. ISO 22810 is paywalled and only its abstract is public. The test is covered in this Codex's entry on the water-resistant watch."
],
"related": [
"water-resistant-watch",
"divers-watch",
"gasket",
"caseback"
],
"sources": [
{
"tier": 1,
"citation": "Bureau international des poids et mesures (BIPM), The International System of Units (SI), 9th edition (2019), English text",
"url": "https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "BIPM, news item \"Updated SI Brochure clarifies the status of non-SI units\", 4 June 2026",
"url": "https://www.bipm.org/en/-/2026-06-04-updated-si-brochure-clarifies-the-status-of-non-si-units",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Seiko Watch Corporation, customer service FAQ, \"Water Resistance\"",
"url": "https://www.seikowatches.com/us-en/customerservice/faq/general-information-8",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 22810:2010, Horology - Water-resistant watches, edition 1, published August 2010, status Published",
"url": "https://www.iso.org/standard/45334.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium",
"autolink": false,
"autolink_note": "\"Bar\" is a common English word and would link on unrelated uses elsewhere on the site."
},
{
"term": "Leap second",
"slug": "leap-second",
"aliases": [
"leap seconds"
],
"domain": "measurement",
"status": "verified",
"short": "A one-second insertion into UTC that keeps civil time in step with the Earth's rotation; a watch has no way of knowing one happened.",
"full": [
"The IERS, which decides when one is needed, defines the device simply: \"Leap seconds are used to adjust the time scale UTC to the apparent motion of the Sun, i.e. to Earth rotation\", the purpose being to hold the difference UT1 minus UTC within 0.9 seconds. BIPM, which produces the time scale, states that \"UTC is obtained from International Atomic Time (TAI) by the insertion of leap seconds\", made \"according to the advice of the International Earth Rotation and Reference Systems Service (IERS)\".",
"Insertions are announced in IERS Bulletin C, issued twice a year by the IERS Earth Orientation Centre. Bulletin C Number 72, published on 6 July 2026, states that \"NO leap second will be introduced at the end of December 2026\" and gives UTC minus TAI as −37 s, a value in force since 1 January 2017, the date the most recent leap second took effect.",
"The 2035 decision is narrower than it is usually described. Resolution 4 of the 27th CGPM (2022), \"On the use and future development of UTC\", decides that \"the maximum value for the difference (UT1-UTC) will be increased in, or before, 2035\", and asks the CIPM, consulting the ITU, to propose a new maximum value ensuring the continuity of UTC \"for at least a century\" and to bring a resolution to the 28th CGPM in 2026. What this Codex does not do: say that the CGPM abolished the leap second. The words \"leap second\" appear only in the preamble, which notes that \"the introduction of leap seconds creates discontinuities that risk causing serious malfunctions in critical digital infrastructure\".",
"For a watch the consequence follows from the mechanism. A leap second is inserted into a time scale computed at the BIPM and announced in a bulletin; a watch running on its own oscillator receives nothing, keeps counting undisturbed, and ends one second from civil time until it is reset by hand."
],
"related": [
"coordinated-universal-time",
"atomic-clock",
"second",
"radio-controlled-watch"
],
"sources": [
{
"tier": 1,
"citation": "International Earth Rotation and Reference Systems Service (IERS), Glossary entry \"leap second\"",
"url": "https://www.iers.org/SharedDocs/Glossareintraege/EN/L/leapSecond",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "IERS Earth Orientation Centre, IERS Bulletin C Number 72, published 6 July 2026",
"url": "https://datacenter.iers.org/data/16/bulletinc-072.txt",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "BIPM, \"Time metrology\" (BIPM Time Department)",
"url": "https://www.bipm.org/en/time-metrology",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Resolution 4 of the 27th CGPM (2022), \"On the use and future development of UTC\"",
"url": "https://www.bipm.org/en/cgpm-2022/resolution-4",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Atomic clock",
"slug": "atomic-clock",
"aliases": [
"caesium clock",
"cesium clock"
],
"domain": "measurement",
"status": "verified",
"short": "A clock whose frequency is taken from an atomic transition; the caesium-133 transition is what defines the SI second.",
"full": [
"An atomic clock counts a transition inside an atom instead of the swing of a balance. The transition in question is written into the SI: BIPM's SI Brochure fixes the caesium frequency, \"the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz\". NIST states the same history plainly: \"The resonance frequency of the hyperfine splitting in cesium has defined the second since 1967.\" This Codex's entry on the second sets out that definition in full.",
"NIST describes how its caesium fountain standards find that frequency. \"Six infrared laser beams then are directed at right angles to each other at the center of the chamber. The lasers slow down the atoms, and a cold cloud of cesium atoms forms\"; the cloud is launched upward through a microwave cavity and falls back through it, and the microwave frequency that excites the most atoms is \"the natural resonance frequency of the cesium atom (9,192,631,770 Hz), or the frequency used to define the SI second\". NIST states that with such clocks \"the definition of the second can now be realized with an uncertainty approaching 1×10-16\".",
"These clocks are the reference behind ordinary civil time rather than instruments anyone wears. NIST notes that \"A primary frequency standard contributes to the calibration of the official international time scale Coordinated Universal Time (UTC), and to its local realization UTC(NIST) which is synthesized and distributed from the NIST laboratories in Boulder\", and the CGPM's own definition has TAI as \"a continuous time scale produced by the BIPM based on the best realizations of the SI second\". A radio-controlled watch is not an atomic clock; it is a watch that receives a signal traceable to one."
],
"related": [
"second",
"coordinated-universal-time",
"radio-controlled-watch",
"thermocompensated-quartz"
],
"sources": [
{
"tier": 1,
"citation": "Bureau international des poids et mesures (BIPM), The International System of Units (SI), 9th edition (2019), English text",
"url": "https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "NIST, Time and Frequency Division, \"NIST's Cesium Fountain Atomic Clocks\"",
"url": "https://www.nist.gov/pml/time-and-frequency-division/time-realization/cesium-fountain-atomic-clocks",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Resolution 2 of the 26th CGPM (2018), \"On the definition of time scales\"",
"url": "https://www.bipm.org/en/committees/cg/cgpm/26-2018/resolution-2",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Coordinated Universal Time",
"slug": "coordinated-universal-time",
"aliases": [
"UTC"
],
"domain": "measurement",
"status": "verified",
"short": "The world's reference time scale, produced by BIPM: the same rate as atomic time TAI, but offset from it by a whole number of seconds.",
"full": [
"Resolution 2 of the 26th CGPM (2018) gives the definitions. TAI \"is a continuous time scale produced by the BIPM based on the best realizations of the SI second\", and UTC is \"a time scale produced by the BIPM with the same rate as TAI, but differing from TAI only by an integral number of seconds\". The resolution adds that \"UTC produced by the BIPM, based on TAI, is the only recommended time scale for international reference and the basis of civil time in most countries\". The whole-second offset is what allows an atomic time scale to stay close to the turning Earth.",
"The Earth is the reason the offset changes. BIPM states that \"UTC is obtained from International Atomic Time (TAI) by the insertion of leap seconds\", on IERS advice, \"to ensure approximate agreement with the time derived from the rotation of the Earth\". The 2018 resolution notes that \"users can derive the rotation angle of the Earth by applying to UTC the observed or predicted values of UT1 - UTC, as provided by the IERS\". The Royal Observatory Greenwich puts the tolerance in numbers: the difference is made \"in order to keep UTC within 0.9 seconds of the time determined by the mean position of the Sun (UT1)\".",
"\"GMT\" is a separate matter. The Royal Observatory records that \"From 1884 until 1972, GMT was the international standard of civil time. Though it has now been replaced by Coordinated Universal Time (UTC)\", UTC being \"the modern equivalent of Greenwich Mean Time (GMT), which is never more than half a second different from it\". On a watch dial, by contrast, \"GMT\" is a trade label for a second time-zone display: it says nothing about which time scale the watch is set to, and nothing about UTC. This Codex's entry on the dual-time watch covers that function."
],
"related": [
"leap-second",
"atomic-clock",
"dual-time",
"world-time"
],
"sources": [
{
"tier": 1,
"citation": "Resolution 2 of the 26th CGPM (2018), \"On the definition of time scales\"",
"url": "https://www.bipm.org/en/committees/cg/cgpm/26-2018/resolution-2",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "BIPM, \"Time metrology\" (BIPM Time Department)",
"url": "https://www.bipm.org/en/time-metrology",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, Royal Observatory Greenwich, \"Which time is it?\"",
"url": "https://www.rmg.co.uk/stories/time/which-time-it",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, \"What is Greenwich Mean Time (GMT) - and why does it matter?\"",
"url": "https://www.rmg.co.uk/stories/time/greenwich-mean-time-gmt",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Case",
"slug": "watch-case",
"aliases": [
"watch case"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "The rigid outer housing that carries a watch's movement, dial and glass and, on a sealed watch, is what keeps water out.",
"full": [
"No standards body, museum or law opened for this entry defines what a watch case is. ISO's own vocabulary for the trade, ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published in February 2026 by ISO/TC 114/SC 9, says of itself only that it \"defines the principal terms used in horology\". Only that scope statement is public, so whether \"case\" is among those principal terms cannot be checked here.",
"ISO writes about the case constantly without any public text saying what it is. ISO 23160:2011, Watch cases and accessories — Tests of the resistance to wear, scratching and impacts, \"specifies tests for the evaluation of the resistance of watch cases and their bracelets to wear, scratching and impacts occurring when wearing the watch\". ISO's own news release on water-resistant watches puts the case at the centre of the claim a buyer reads: if a watch is marked water resistant to 30 metres, \"this means that for all aquatic activities down to a depth of 30 meters, the watch case should not leak.\" The case is the thing tested and the thing that must not leak. Whether ISO 6426-2:2026 defines it among its \"principal terms\" cannot be checked here, because only that standard's scope statement is public.",
"The Swiss industry's own norms come closer and still stop short of a public definition. The list of available NIHS standards published by the Federation of the Swiss Watch Industry, valid from April 2026, includes NIHSG 60-01, Boîtes – Terminologie (cases, terminology; first issued 1967, revised 2022). A terminology norm for the watch case therefore exists; as with the ISO vocabulary, only its title is public, so its wording is not quoted here."
],
"related": [
"caseback",
"bezel",
"crystal",
"water-resistant-watch"
],
"sources": [
{
"tier": 1,
"citation": "ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published February 2026, ISO/TC 114/SC 9 (catalogue page; standard text not public)",
"url": "https://www.iso.org/standard/88512.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 23160:2011, Watch cases and accessories — Tests of the resistance to wear, scratching and impacts, edition 1, published June 2011, ISO/TC 114/SC 6",
"url": "https://www.iso.org/standard/45522.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO, news release \"ISO standard for water-resistant watches makes 'huge splash'\", November 2010",
"url": "https://www.iso.org/news/2010/11/Ref1367.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-27",
"review_due": "2027-03-26",
"confidence": "high",
"autolink": false,
"autolink_note": "\"Case\" is too common an English word to link automatically wherever it appears."
},
{
"term": "Bezel",
"slug": "bezel",
"aliases": [
"rotating bezel",
"dive bezel"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "The ring on the front of a watch case; fixed, it retains the glass, and on a divers' watch it turns to time a dive.",
"full": [
"The British Horological Institute, a professional body for watch and clock makers rather than a standards-setting authority, defines the word in the glossary of its Practical Clock and Watch Servicing Distance Learning Course Technician Grade: a bezel is \"That part of a watch or clock which holds the glass (or crystal) protecting the dial and hands.\" That describes the fixed bezel, and it is the only definition of the term this Codex could read in a source it is willing to cite.",
"A bezel can also be a structural, threaded component. Rolex's own account of its Oyster case states that \"A system of screwing down the bezel, case back and winding crown against the middle case ensured that the case was hermetically sealed\", and that \"The bezel on the original Oyster case was fluted, allowing it to be screwed down onto the middle case using a tool exclusive to Rolex.\" The Swiss industry treats the bezel as a case part with its own dimensions: the Federation of the Swiss Watch Industry's list of available NIHS standards includes NIHSG 60-21, Boîtes rondes étanches – Carrure-lunette (partie lunette).",
"The open question. The rotating bezel is the one form of bezel a standard cares about, and its clause has not been read. ISO 6425:2018, Horology — Divers' watches, edition 4, published October 2018, applies to watches \"equipped with a secured measuring system to indicate the diving time, which is visible in darkness\". On a conventional divers' watch that secured system is the rotating bezel, but the standard's requirements text is paywalled, so the rule that such a bezel may turn in one direction only is neither quoted nor attributed to ISO here."
],
"related": [
"divers-watch",
"watch-case",
"crystal",
"dial"
],
"sources": [
{
"tier": 2,
"citation": "British Horological Institute, Practical Clock and Watch Servicing Distance Learning Course Technician Grade, introduction and lesson 1, section 16 \"Glossary of horological terms\"",
"url": "https://bhi.co.uk/wp-content/uploads/2023/01/Binder1-combined-intro-and-lesson-1.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Rolex, \"Behind the crown — Mastering waterproofness\" (the company's own account of the Oyster case)",
"url": "https://www.rolex.com/en-us/about-rolex/behind-the-crown/mastering-waterproofness",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 6425:2018, Horology — Divers' watches, edition 4, published October 2018, ISO/TC 114/SC 3 (catalogue page; standard text not public)",
"url": "https://www.iso.org/standard/66517.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Dial",
"slug": "dial",
"aliases": [
"watch dial"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "The face of a watch: the plate carrying the markings against which the hands are read.",
"full": [
"Nothing this Codex could open defines the dial. The British Horological Institute's teaching glossary, in its Practical Clock and Watch Servicing Distance Learning Course Technician Grade, has no entry for \"dial\" at all; the Institute is a professional body rather than a standards authority, and even it uses the word only inside another definition, describing a bezel as the part \"which holds the glass (or crystal) protecting the dial and hands.\" The dial is assumed known.",
"Two bodies have written a definition that is not published in full. ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published February 2026 by ISO/TC 114/SC 9, states only that it \"defines the principal terms used in horology\". The Federation of the Swiss Watch Industry's list of available NIHS standards, valid from April 2026, includes NIHSG 65-01, Cadrans – Terminologie (dials, terminology, first issued in 1961 and revised in 2022), together with NIHSG 65-21 on the dimensions of dial holes. In both cases only the titles are public, so neither wording is quoted here.",
"What can be documented is institutional usage. The Science Museum Group's record for a watch by Edward East, London, c.1680, held by the Worshipful Company of Clockmakers, reads: \"Brass case, covered in leather, possibly shark-skin. White enamel dial, with hands missing.\" A national collection uses \"dial\" as a plain descriptive term for the marked plate the hands sweep, three and a half centuries after the object was made, without ever needing to say what one is."
],
"related": [
"luminous-material",
"radium-dial",
"guilloche",
"watch-case"
],
"sources": [
{
"tier": 2,
"citation": "British Horological Institute, Practical Clock and Watch Servicing Distance Learning Course Technician Grade, introduction and lesson 1, section 16 \"Glossary of horological terms\"",
"url": "https://bhi.co.uk/wp-content/uploads/2023/01/Binder1-combined-intro-and-lesson-1.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published February 2026, ISO/TC 114/SC 9 (catalogue page; standard text not public)",
"url": "https://www.iso.org/standard/88512.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Science Museum Group Collection, object record co8557659, \"Watch with a later case and dial by Edward East\" (Clockmakers' Museum No. 46, Worshipful Company of Clockmakers)",
"url": "https://collection.sciencemuseumgroup.org.uk/objects/co8557659/watch-with-a-later-case-and-dial-by-edward-east",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Crown",
"slug": "crown",
"aliases": [
"winding crown",
"screw-down crown"
],
"domain": "mechanism",
"status": "verified",
"short": "The knob outside a watch case, turned to wind the mainspring and set the hands, and on sealed watches screwed down against the case.",
"full": [
"The British Horological Institute (a professional horological body, not a standards authority) defines the component in the glossary of its Practical Clock and Watch Servicing Distance Learning Course Technician Grade, under the headword \"Button\": \"The external component of a watch used to wind the watch and set the hands to time. Also called the crown.\" Two jobs, winding and setting, in one part that the wearer is the only person who ever touches deliberately.",
"On a sealed watch the crown is also a stopper. Rolex's own account of its Oyster case states that \"A system of screwing down the bezel, case back and winding crown against the middle case ensured that the case was hermetically sealed\", and records its later work in the company's own words: \"In 1953, Rolex introduced the Twinlock winding crown, which incorporated a patented system with a double seal\", followed in 1970 by \"the Triplock winding crown, comprising an additional sealed zone\". Omega, writing about its own watches, states the consequence for an owner plainly: \"If your watch is equipped with a screw-in crown, always screw it in after handling it.\"",
"The Swiss industry norms the part without publishing the definition. The Federation of the Swiss Watch Industry's list of available NIHS standards, valid from April 2026, includes NIHSG 63-01, Couronnes, tubes de couronnes, poussoirs latéraux pour montres, correcteurs latéraux pour montres – Terminologie, a terminology norm covering crowns and crown tubes, first issued in 1967 and revised in 2022. The list gives titles only, so no definition text was read here."
],
"related": [
"keyless-works",
"hand-winding",
"gasket",
"water-resistant-watch"
],
"sources": [
{
"tier": 2,
"citation": "British Horological Institute, Practical Clock and Watch Servicing Distance Learning Course Technician Grade, introduction and lesson 1, section 16 \"Glossary of horological terms\"",
"url": "https://bhi.co.uk/wp-content/uploads/2023/01/Binder1-combined-intro-and-lesson-1.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Rolex, \"Behind the crown — Mastering waterproofness\" (the company's own account of the Oyster case)",
"url": "https://www.rolex.com/en-us/about-rolex/behind-the-crown/mastering-waterproofness",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, \"Caring for your OMEGA\", customer service FAQ (the company's own statements about its watches)",
"url": "https://www.omegawatches.com/en-us/customer-service/faq/caring-for-your-omega",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Lug",
"slug": "lug",
"aliases": [
"lug width",
"horn"
],
"domain": "mechanism",
"status": "verified",
"short": "One of the projections from a watch case that hold the strap or bracelet; the gap between a facing pair is the lug width, quoted in millimetres.",
"full": [
"The British Horological Institute, a professional body rather than a standards authority, defines the term in the glossary of its Practical Clock and Watch Servicing Distance Learning Course Technician Grade: lugs are \"Projections on wrist watch cases supporting the strap or bracelet.\" They belong to the case and not to the band, and they exist only because a wristwatch has to be fastened to a wrist.",
"The measurement that matters to a wearer is the distance between a facing pair, because a strap or bracelet has to be exactly that wide to fit. Manufacturers publish it in millimetres. Omega's own specification for the Speedmaster Moonwatch Professional 42 mm, reference 310.30.42.50.01.002, gives \"Between lugs: 20 mm\" and, separately, \"Lug-to-lug: 47.50 mm\". The page gives the two figures without saying what either governs; on this Codex's reading the first is the fitting width a band must match and the second is the overall length of the case across its lugs. They are two different measurements and are easily confused.",
"The fitting itself is normed in Switzerland, though the norm's text has not been read here. The Federation of the Swiss Watch Industry's list of available NIHS standards, valid from April 2026, includes NIHS 60-81, Timekeeping instruments – Wristwatches – Dimensions of bracelet-to-case fastening elements (1998), and NIHS 60-85, Timekeeping instruments – Wristwatch-cases – Fixing dimensions of non-spring-bar types (2001). Neither text has been read here; their titles establish that the lug fitting is a normed dimension and that not every fitting uses a spring bar."
],
"related": [
"bracelet",
"strap",
"watch-case",
"caseback"
],
"sources": [
{
"tier": 2,
"citation": "British Horological Institute, Practical Clock and Watch Servicing Distance Learning Course Technician Grade, introduction and lesson 1, section 16 \"Glossary of horological terms\"",
"url": "https://bhi.co.uk/wp-content/uploads/2023/01/Binder1-combined-intro-and-lesson-1.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, official specification for Speedmaster Moonwatch Professional 42 mm, reference 310.30.42.50.01.002",
"url": "https://www.omegawatches.com/en-us/watch-omega-speedmaster-moonwatch-professional-co-axial-master-chronometer-chronograph-42-mm-31030425001002",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Caseback",
"slug": "caseback",
"aliases": [
"case back",
"display caseback"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "The closing panel on the back of a watch case, screwed or pressed into place, and sometimes made transparent to show the movement.",
"full": [
"No source this Codex could open defines the back of a watch case. ISO's trade vocabulary, ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published February 2026 by ISO/TC 114/SC 9, states only that it \"defines the principal terms used in horology\"; only that scope statement is public, so whether the caseback is among those terms cannot be checked. The Federation of the Swiss Watch Industry's list of available NIHS standards comes closer than anything else found: it includes NIHSG 60-03, Boîtes étanches – Filetages – Fonds – Terminologie, the terminology of the threads and backs of sealed cases. A terminology norm naming the fond exists; its text has not been read here either.",
"What is documented is how backs are held on. Rolex's own account of the Oyster case describes a back that screws: \"The back of the Oyster case was edged with fine fluting – as it still is today – enabling it to be screwed down hermetically against the middle case\", as part of \"A system of screwing down the bezel, case back and winding crown against the middle case\".",
"A caseback can also be a window. Omega's own specification for one Speedmaster Moonwatch Professional reference, 311.33.42.30.01.002, lists the back simply as \"Transparent caseback,\" a panel through which the movement can be seen, offered alongside solid-backed versions of the same watch. No authority read for this entry sets out or names the types of caseback, so the trade's ordinary distinctions between screwed, screw-down and pressed-in backs are recorded here as usage rather than as defined terms."
],
"related": [
"watch-case",
"gasket",
"skeletonised",
"water-resistant-watch"
],
"sources": [
{
"tier": 1,
"citation": "ISO 6426-2:2026, Horological vocabulary — Part 2: Technical and commercial definitions, edition 3, published February 2026, ISO/TC 114/SC 9 (catalogue page; standard text not public)",
"url": "https://www.iso.org/standard/88512.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Rolex, \"Behind the crown — Mastering waterproofness\" (the company's own account of the Oyster case)",
"url": "https://www.rolex.com/en-us/about-rolex/behind-the-crown/mastering-waterproofness",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, official specification for Speedmaster Moonwatch Professional Steel Transparent caseback, reference 311.33.42.30.01.002",
"url": "https://www.omegawatches.com/en-us/watch-omega-speedmaster-moonwatch-professional-chronograph-42-mm-31133423001002",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Gasket",
"slug": "gasket",
"aliases": [
"O-ring",
"seal"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "The compressible ring or washer that seals a joint in a watch case; it is what makes a watch water-resistant, and it ages.",
"full": [
"No definition of the word was found in any standard, museum record or law opened for this entry. The clearest functional account comes instead from a manufacturer writing about its own watches. Omega states: \"The water resistance of a watch is ensured by gaskets placed between the crown, the pushers, the crystal, and the watch case.\" That is the whole mechanism. A case is not watertight in itself; its joints are sealed, and the gaskets are what seal them.",
"Omega is equally explicit, again about its own product, that the seal is a consumable: \"These gaskets deteriorate over time under the influence of external factors such as temperature variations, pollution or chemicals and must be regularly replaced to guarantee the water resistance of the watch.\" Its description of a complete service says that \"all gaskets ensuring the water resistance are replaced\". These are the brand's statements about its own watches, not an independent requirement on anyone else's.",
"The Swiss industry norms the gasket's seat rather than the gasket's meaning. The Federation of the Swiss Watch Industry's list of available NIHS standards includes NIHSG 62-02, Joints toriques – Logements (O-ring gaskets, housings; 1968, revised 2022), NIHSG 62-04, Joints plats – Logements (flat gaskets, housings), and NIHS 61-12, Mineral and sapphire watch-glasses – Part 2: Assembly to the case by adhesive or using a gasket (2003). Testing the result is a separate matter, governed by ISO 22810:2010, Horology — Water-resistant watches, which \"establishes the requirements and specifies the test methods used to verify the water resistance of watches\"."
],
"related": [
"water-resistant-watch",
"crown",
"caseback",
"bar"
],
"sources": [
{
"tier": 1,
"citation": "OMEGA, \"Caring for your OMEGA\", customer service FAQ (the company's own statements about its watches)",
"url": "https://www.omegawatches.com/en-us/customer-service/faq/caring-for-your-omega",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, \"Complete OMEGA watch service: the main steps\" (the company's own description of its service)",
"url": "https://www.omegawatches.com/en-us/customer-service/interventions-and-prices/complete-service",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 22810:2010, Horology — Water-resistant watches, edition 1, published August 2010, ISO/TC 114/SC 3",
"url": "https://www.iso.org/standard/45334.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Bracelet",
"slug": "bracelet",
"aliases": [
"watch bracelet",
"metal bracelet"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "A watch band made of linked metal components, attached to the case at the lugs; ISO uses the same word for any watch band.",
"full": [
"In everyday trade use a bracelet is the metal band of a watch (articulated links closed by a clasp), as against a strap of leather, rubber or fabric. Manufacturers hold the two words apart in their own specifications: Omega lists the band of the steel Speedmaster Moonwatch Professional 42 mm, reference 310.30.42.50.01.002, as \"Bracelet: Steel\", with a \"Foldover clasp with comfort setting\". No standards body, museum or law opened for this entry defines either word, and none of them characterises the distinction.",
"ISO, awkwardly for that convention, uses \"bracelet\" for the band whatever it is made of. ISO 23160:2011, Watch cases and accessories — Tests of the resistance to wear, scratching and impacts, \"specifies tests for the evaluation of the resistance of watch cases and their bracelets to wear, scratching and impacts occurring when wearing the watch\", and adds that \"certain tests can be applied to the watch case only, to the complete or partial bracelet, or to specially prepared samples\". The band is a tested component; it is not a defined one.",
"The Swiss norms use the same word. The Federation of the Swiss Watch Industry's list of available NIHS standards includes NIHS 60-81, Timekeeping instruments – Wristwatches – Dimensions of bracelet-to-case fastening elements (1998), which normalises the fitting between band and case under the word \"bracelet\". The British Horological Institute's teaching glossary (the work of a professional body, not a standards authority) has no entry for either \"bracelet\" or \"strap\"; it names them only in passing, defining lugs as \"Projections on wrist watch cases supporting the strap or bracelet.\""
],
"related": [
"strap",
"lug",
"watch-case"
],
"sources": [
{
"tier": 1,
"citation": "OMEGA, official specification for Speedmaster Moonwatch Professional 42 mm, reference 310.30.42.50.01.002",
"url": "https://www.omegawatches.com/en-us/watch-omega-speedmaster-moonwatch-professional-co-axial-master-chronometer-chronograph-42-mm-31030425001002",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 23160:2011, Watch cases and accessories — Tests of the resistance to wear, scratching and impacts, edition 1, published June 2011, ISO/TC 114/SC 6",
"url": "https://www.iso.org/standard/45522.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Liste des normes disponibles valable dès avril 2026\" (list of available NIHS standards of the Swiss watch industry)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "British Horological Institute, Practical Clock and Watch Servicing Distance Learning Course Technician Grade, introduction and lesson 1, section 16 \"Glossary of horological terms\"",
"url": "https://bhi.co.uk/wp-content/uploads/2023/01/Binder1-combined-intro-and-lesson-1.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Strap",
"slug": "strap",
"aliases": [
"watch strap",
"leather strap"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "A watch band of leather, rubber or fabric, fastened to the case at the lugs; distinguished in trade use from a metal bracelet.",
"full": [
"No standards body, museum or law opened for this entry defines a watch strap, and nor does the trade's own teaching material. The British Horological Institute (a professional horological body rather than a standards authority) mentions straps in the glossary of its Practical Clock and Watch Servicing Distance Learning Course Technician Grade only inside another entry, defining lugs as \"Projections on wrist watch cases supporting the strap or bracelet.\" That pairing is the whole of the distinction: a strap and a bracelet are alternatives at the same fitting, and neither is defined.",
"Manufacturers' own specifications show what the word carries in practice. Omega's specification for Speedmaster Moonwatch Professional reference 311.33.42.30.01.002 lists a \"Leather strap\" whose surface is \"Alligator leather\" and underside \"Non-grained calf leather\", closed by a \"Foldover clasp\". Other materials are described the same way: the Seiko Museum's account of the 1975 Professional Diver's 600m watch, written by its development leader and designer Taro Tanaka, records that the team \"adopted polyurethane for the material of the strap, in place of the PVC plastic\".",
"The Federation of the Swiss Watch Industry publishes the Illustrated Professional Dictionary of Horology, \"originally compiled by G.-A. Berner and published in 1961\" and now carrying \"more than 6,000 entries\", which FH calls \"a genuine reference for the watchmaking industry and a valuable translation tool\". It is a trilingual dictionary rather than a standard, and its individual entries could not be opened while this page was prepared, so nothing is quoted from it here. On the evidence gathered, \"strap\" is an ordinary word the industry uses precisely and has never had to define."
],
"related": [
"bracelet",
"lug",
"watch-case",
"divers-watch"
],
"sources": [
{
"tier": 2,
"citation": "British Horological Institute, Practical Clock and Watch Servicing Distance Learning Course Technician Grade, introduction and lesson 1, section 16 \"Glossary of horological terms\"",
"url": "https://bhi.co.uk/wp-content/uploads/2023/01/Binder1-combined-intro-and-lesson-1.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, official specification for Speedmaster Moonwatch Professional Steel Transparent caseback, reference 311.33.42.30.01.002",
"url": "https://www.omegawatches.com/en-us/watch-omega-speedmaster-moonwatch-professional-chronograph-42-mm-31133423001002",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "THE SEIKO MUSEUM GINZA, Seiko Milestones, \"Professional Diver's 600m Watch\", article by Taro Tanaka, development leader and designer",
"url": "https://museum.seiko.co.jp/en/seiko_history/milestone/milestone_08/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse (FH), \"Professional dictionary\", the Illustrated Professional Dictionary of Horology",
"url": "https://www.fhs.swiss/eng/dictionary.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Lever escapement",
"slug": "lever-escapement",
"aliases": [
"Swiss lever escapement",
"detached lever escapement",
"club tooth escapement"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "The escapement used in almost all mechanical watches, in which a pivoted lever locks and releases the escape wheel and impulses the balance.",
"full": [
"A lever escapement stands between the geared train and the balance. A pivoted lever, the pallet fork, carries two pallets that alternately lock and release the escape wheel, and at each release the lever pushes the balance on through a pin on the balance staff. In the earliest form the escape wheel's \"pointed teeth\", in the Seiko Museum Ginza's words, \"would push against the pallet stones of the anchor\". Because the balance is joined to the train only for that brief push and swings free through the rest of its arc, the escapement is called detached.",
"The invention is attributed to the English watchmaker Thomas Mudge, but the sources do not agree on the year. The Seiko Museum Ginza states: \"Around 1756, the English watchmaker Thomas Mudge invented a detached lever escapement (ratchet tooth lever escapement).\" The Antiquarian Horological Society (a learned society rather than an issuing authority) dates it earlier, listing under 1754 \"Thomas Mudge's Experimental Marine timekeeper, the first example of the detached lever escapement\", and separately under 1769 \"Thomas Mudge completes his detached lever watch for Queen Charlotte.\" The Royal Collection Trust's record for that watch says it \"incorporates the earliest known example of the lever escapement\". This Codex reports the disagreement rather than choosing a year.",
"The pointed-tooth original was later displaced by the club tooth escapement, whose teeth, in the museum's words, \"resembling golf clubs\" could \"absorb the impulse of the escape wheel with the flat surface\".",
"What this Codex does not do: cite a standard here. The Federation of the Swiss Watch Industry's published list of available NIHS norms contains no norm titled for the escapement, the anchor or the escape wheel. The account above rests on museum and learned-society records, named in the prose."
],
"related": [
"escapement",
"pallet-fork",
"escape-wheel",
"balance-wheel"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The lever escapement that led to modern developments\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces06/",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Antiquarian Horological Society, \"Historical timeline\"",
"url": "https://www.ahsoc.org/resources/historical-timeline/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Collection Trust, collection record RCIN 63759, Thomas Mudge, \"Queen Charlotte's Lever Watch and Pedestal\"",
"url": "https://www.rct.uk/collection/63759/queen-charlottes-lever-watch-and-pedestal",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Co-axial escapement",
"slug": "co-axial-escapement",
"aliases": [
"Co-Axial escapement",
"coaxial escapement"
],
"domain": "mechanism",
"status": "verified",
"short": "A detached escapement patented by George Daniels in 1979-80 that impulses the balance directly, put into series production by Omega from 1999.",
"full": [
"The primary document is a patent. The European Patent Office's publication server carries EP 0 018 796 A3, Watches, clocks and chronometers and escapements therefor, in the name of George Daniels, filed on 25 April 1980 with a priority date of 30 April 1979 (GB 7915006). Its own opening words set out the object: \"The invention relates to a detached escapement which preferably does not require oil to be applied to the escape wheel. The escapement has an escape wheel (10;30), a balance wheel and a pivoted lever (14;37) arranged so that during each movement of the balance wheel in one direction of rotation an impulse is applied direct to an element (25;33) attached to the balance wheel.\"",
"Omega's own chronicle dates the commercial release to 12 April 1999 and calls the result \"the industry's first practical new watch escapement in some 250 years\", one that \"produces less friction and requires less lubrication, making it far more reliable than traditional movements\". Elsewhere Omega states that the design \"used smaller contact surfaces, which meant less friction, less lubrication and greater reliability\". Those are the company's own claims about its own product, not figures from a neutral testing body.",
"An Omega press release held in Swatch Group's online archive under 2010 supplies the calibre numbers: \"When Omega launched its Co-Axial calibre 2500 in 1999, the entire mechanical watch industry was put on notice\", and, of the 2007 calibre 8500, \"For the first time, the company built the entire movement around the Co-Axial Escapement and every one of its 202 parts was developed and produced in-house.\" The same release quotes Daniels on his escapement: \"It is intended to sustain the public affection for the mechanical watch during the 21st century.\""
],
"related": [
"escapement",
"lever-escapement",
"escape-wheel",
"pallet-fork"
],
"sources": [
{
"tier": 1,
"citation": "European Patent Office publication server, EP 0 018 796 A3, \"Watches, clocks and chronometers and escapements therefor\", applicant George Daniels, filed 25.04.1980, priority 30.04.1979 (GB 7915006)",
"url": "https://data.epo.org/publication-server/rest/v1.2/publication-dates/19810128/patents/EP0018796NWA3/document.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, Chronicle: \"1999: OMEGA introduces the Co-Axial watch escapement\"",
"url": "https://www.omegawatches.com/chronicle/1999-a-revolutionary-new-escapement",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, \"The Co-Axial Escapement\" (World of OMEGA: Watchmaking / Precision)",
"url": "https://www.omegawatches.com/world-of-omega/watchmaking/precision/watchmaking/the-co-axial-escapement",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swatch Group archive (2010), OMEGA press release \"Omega's Co-Axial Story\"",
"url": "https://www.swatchgroup.com/en/services/archive/2010/omegas-co-axial-story",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Pallet fork",
"slug": "pallet-fork",
"aliases": [
"pallet lever",
"anchor"
],
"domain": "mechanism",
"status": "verified",
"short": "The pivoted lever in a lever escapement whose two pallets lock and release the escape wheel and carry its impulse to the balance.",
"full": [
"The pallet fork is the pivoted part that sits between the escape wheel and the balance. It carries two pallets that take the escape wheel's teeth in turn, holding the wheel still and then letting it move on one step, and it passes that step to the balance through a pin. Its names vary with the writer: the Seiko Museum Ginza describes the escape wheel's teeth pushing \"against the pallet stones of the anchor\", while the published European patent application EP 3 185 083 A1, Mechanical timepiece mechanism with anchor escapement, filed on 23 December 2015, speaks of \"a pallet-lever 4 arranged to move alternately into abutment with two banking elements 24, 25,\" the fixed stops that limit its travel at each end of its swing.",
"The pallets themselves are normally jewels. The same museum, describing the cheaper pin-lever escapement, says metal pins were used \"in place of the rubies that were used in the club tooth escapement to reduce wear on the anchor pallets and impulse pin\": in the ordinary lever escapement the working faces are set stones, not steel.",
"No standards body defines the part. The Federation of the Swiss Watch Industry's published list of available NIHS norms for the Swiss watch industry contains no norm titled for the anchor, the pallet lever or the escape wheel, and ISO's horological vocabulary is paywalled. What is quoted above is therefore a museum record and a patent application: a primary record of how the part is described, not a normative definition."
],
"related": [
"escapement",
"lever-escapement",
"escape-wheel",
"jewel"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The lever escapement that led to modern developments\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces06/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The pin-lever escapement that brought the watch to the masses\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces09/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European Patent Office, Global Patent Index record for EP 3 185 083 A1, \"Mechanical timepiece mechanism with anchor escapement\", application EP 15202458, filed 23.12.2015, published 28.06.2017",
"url": "https://data.epo.org/gpi/EP3185083A1",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Escape wheel",
"slug": "escape-wheel",
"aliases": [
"escapement wheel"
],
"domain": "mechanism",
"status": "verified",
"short": "The toothed wheel at the end of a watch's train that the pallet fork locks and releases, passing the train's force on to the balance.",
"full": [
"The escape wheel is the wheel the escapement acts on. Driven by the gear train, it is held still by one pallet of the pallet fork, released, and caught again by the other, so that the train advances one tooth at a time and the balance receives one push per release. The shape of the teeth defines the variety of escapement: the Seiko Museum Ginza describes the earliest lever form as a ratchet tooth design whose \"pointed teeth\" \"would push against the pallet stones of the anchor\", later replaced by the club tooth escapement with teeth \"resembling golf clubs\" that \"absorb the impulse of the escape wheel with the flat surface\", reducing wear.",
"The contact between tooth and pallet is where a mechanical watch loses most of its energy to friction, and it is the part of the movement that depends most on oil. George Daniels' patent application makes that the whole point of his design: \"The invention relates to a detached escapement which preferably does not require oil to be applied to the escape wheel.\"",
"Materials have changed. The Seiko Museum Ginza states that \"An increasing number of manufacturers are using silicon materials not only for the hairspring, but also for the escape wheel and pallet fork\", because \"Silicon has a smooth surface and is both hard and light, which means that it can reduce accuracy errors caused by friction while also reducing the frequency of oiling.\" Speaking for its own company, the museum adds: \"Although silicon is hard, it is brittle under impact, and for this reason Seiko does not use it.\" Seiko instead \"manufactures its escape wheels and pallet forks from nickel alloys using MEMS (Micro Electrical Mechanical Systems),\" the museum's own account of its company's practice."
],
"related": [
"escapement",
"pallet-fork",
"gear-train",
"lever-escapement"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The lever escapement that led to modern developments\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces06/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The pursuit of even greater precision\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces12/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European Patent Office publication server, EP 0 018 796 A3, \"Watches, clocks and chronometers and escapements therefor\", applicant George Daniels, filed 25.04.1980",
"url": "https://data.epo.org/publication-server/rest/v1.2/publication-dates/19810128/patents/EP0018796NWA3/document.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Hairspring",
"slug": "hairspring",
"aliases": [
"balance spring",
"spiral spring"
],
"domain": "mechanism",
"status": "verified",
"short": "The fine spiral spring that returns the balance wheel and so fixes a mechanical watch's rate; spring and balance together form the oscillator.",
"full": [
"The Seiko Museum Ginza describes the arrangement plainly: \"The balance wheel comprises a fine 'hairspring' fitted into a metal wheel, with one end of the spring fixed to the wheel and the other fixed to the body of the timepiece.\" The spring is what makes the balance an oscillator rather than a freely turning wheel: \"Like the pendulum, the hairspring is isochronous, so the cycle remains unchanged even when the oscillation angle shifts\", and its invention \"made it possible to produce timepieces that could remain accurate even on board a violently rocking ship or when carried about\".",
"Its application to portable timekeepers in 1675 is a genuine primary-history item, and a contested one. The Antiquarian Horological Society (a learned society, not an issuing authority) lists under 1675: \"Christiaan Huygens invents the balance spring for portable timekeepers at the same time as Robert Hooke claims the same invention.\" The Seiko Museum Ginza credits Huygens in the same year, then adds: \"In the same year, the English clockmaker Thomas Tompion also invented his own balance wheel, based on an idea from his friend Robert Hooke.\" The year is agreed; the priority is not.",
"Hairsprings are standardised as components in Switzerland: the Federation of the Swiss Watch Industry's published list of available NIHS norms includes NIHSG 35-10, \"Spiraux – Numérotation CGS\" (1965/2022), and NIHSG 35-15, \"Spiraux normaux – Dimensions de raccordement avec la virole\" (1972/2022).",
"On alloys this entry keeps to a sourced record. The Nobel Foundation's account of the 1920 Nobel Prize in Physics to Charles Edouard Guillaume states that \"In 1896 Charles-Edouard Guillaume succeeded in finding an alloy of nickel and steel that registered almost no change in length and volume as a result of temperature changes.\" That record names invar and scientific instruments, not watch hairsprings, and the composition of any proprietary modern hairspring alloy is not stated here."
],
"related": [
"balance-wheel",
"silicon-hairspring",
"regulator-index",
"isochronism"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"The invention of the balance wheel and the cylinder escapement\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces04/",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Antiquarian Horological Society, \"Historical timeline\"",
"url": "https://www.ahsoc.org/resources/historical-timeline/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Nobel Foundation, \"Charles Edouard Guillaume — Facts\", Nobel Prize in Physics 1920",
"url": "https://www.nobelprize.org/prizes/physics/1920/guillaume/facts/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Regulator (index)",
"slug": "regulator-index",
"aliases": [
"raquette",
"curb pins",
"regulator lever",
"regulator dial"
],
"domain": "mechanism",
"status": "verified",
"short": "An index that changes the active length of the hairspring, and so a watch's rate; the same word also names a separated-dial clock layout.",
"full": [
"In its first sense, the regulator is a small index pivoted on the balance cock that changes how much of the hairspring is free to work. The published European patent application EP 3 502 788 A1, Standalone device for adjusting the active length of a hairspring (application EP 17208988, filed 20 December 2017, published 26 June 2019), describes exactly this arrangement: \"a regulator mounted on a plate with a cock\", with the balance spring stud holder \"being pivotally mounted on the cock\", and with \"a pivot arm and device for changing the active length of the balance spring by pivoting the regulator\". Shortening the active length makes the balance swing faster; lengthening it slows the watch down.",
"In its second sense the word has nothing to do with that part. A regulator is a precision clock, and the name also attaches to its dial layout. Royal Museums Greenwich catalogues \"An eight-day oak astronomical longcase regulator by George Graham, London, No. 675, circa 1725, Known as 'Graham No.2'\", whose twelve-inch silvered dial carries \"an outer minute circle\" with \"a recessed hour subsidiary dial\" and \"a subsidiary seconds dial with observatory marks,\" the separated indications that the phrase regulator dial still describes on watches today.",
"The two senses are unrelated in function, and this Codex does not pretend the word has one meaning: one is a rate-adjusting part inside a movement, the other a kind of clock and the dial arrangement named after it. Neither is covered by a standard that could be read here. The Federation of the Swiss Watch Industry's published list of available NIHS norms contains no entry for the raquette, the French name for the index."
],
"related": [
"hairspring",
"balance-wheel",
"daily-rate",
"dial"
],
"sources": [
{
"tier": 1,
"citation": "European Patent Office, Global Patent Index record for EP 3 502 788 A1, \"Standalone device for adjusting the active length of a hairspring\", application EP 17208988, filed 20.12.2017, published 26.06.2019",
"url": "https://data.epo.org/gpi/EP3502788A1",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, collection record: \"An eight-day oak astronomical longcase regulator by George Graham, London, No. 675, circa 1725, Known as 'Graham No.2'\"",
"url": "https://www.rmg.co.uk/collections/objects/rmgc-object-246038",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Lift angle",
"slug": "lift-angle",
"aliases": [
"angle of lift"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "The angle through which the escapement drives the balance; a figure a timing machine needs, for which no published standards definition was traced.",
"full": [
"A timing machine does not watch the balance; it listens to the escapement. To turn the sounds it hears into a figure for the balance's amplitude it must know, or measure, how much of the swing the escapement itself drives, the lift angle. Witschi Electronic, a Swiss maker of watch testing instruments, specifies for its WisioScope the \"Determination of actual lift angle and actual amplitude, independent of lift angle\", the \"Measurement of the real lift angle or manual input\", and a range of \"Lift angle 10 to 90° adjustable\". Witschi is cited here only as a manufacturer describing its own instrument, which is what a timing machine expects to be told.",
"No issuing authority defining the term was found. The Federation of the Swiss Watch Industry publishes the list of available NIHS norms for the Swiss watch industry, in the edition valid from April 2026; it contains no entry whose title includes angle de levée. ISO's horological vocabulary does exist: ISO 6426-1:1982, Horological vocabulary — Part 1: Technical and scientific definitions, edition 1, published February 1982 and still listed by ISO as Published, but ISO's catalogue page says only that it gives 20 definitions, and the text is paywalled, so whether lift angle is among them has not been established.",
"What this Codex does not do: quote a definition, or give a lift angle for any calibre. In practice the figure is supplied per movement by its maker, and the only published bound found here is an instrument maker's own adjustment range of 10° to 90°. Until a standards body, a metrology institute or a learned society is found to define the angle, this entry records it as a term in universal workshop use with no authoritative definition traced."
],
"related": [
"amplitude",
"balance-wheel",
"escapement",
"daily-rate"
],
"sources": [
{
"tier": 1,
"citation": "Witschi Electronic Ltd, product page \"WisioScope®\" (lift angle specification)",
"url": "https://www.witschi.com/en/products/wisioscope-2/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Witschi Electronic Ltd, WisioScope data sheet, 9 May 2022",
"url": "https://www.witschi.com/wp-content/uploads/20220509_witschi_wisioscope_data-sheet.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 6426-1:1982, Horological vocabulary — Part 1: Technical and scientific definitions, edition 1, published February 1982",
"url": "https://www.iso.org/standard/12775.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Shock-absorbing device",
"slug": "shock-absorber",
"aliases": [
"shock absorber",
"Incabloc",
"antichoc"
],
"domain": "mechanism",
"status": "verified",
"short": "A sprung mounting for the balance staff's jewel bearings that lets the pivot move and re-centre under impact instead of breaking.",
"full": [
"A shock-absorbing device is the sprung setting that holds the two jewel bearings of the balance staff. Under impact the setting is free to move and then returns to position, so the thin balance pivots are not the part that takes the blow. The Swiss industry has standardised the vocabulary for these parts: the Federation of the Swiss Watch Industry's list of available NIHS norms includes NIHSG 42-01, \"Amortisseurs de chocs – Chatons combinés – Terminologie\" (dated 1963/2022), together with three further NIHSG 42 norms on shock absorbers and companion norms on combined settings.",
"The test such a device exists to pass is ISO 1413:2016, Horology — Shock-resistant wrist watches, edition 3, published April 2016 and listed by ISO as Published; it superseded ISO 1413:1984, which ISO lists as Withdrawn. ISO's catalogue abstract states that the standard \"specifies the minimum requirements for shock-resistant wrist watches and describes the corresponding test method\" and that \"It is based on the simulation of the shock received by a wrist watch while falling from a height of 1 m onto a horizontal wooden floor (an equivalent surface is described in B.1.1).\" The same document is carried in Switzerland as NIHS 91-10 (SN ISO 1413). This Codex's entry on shock-resistance covers the standard itself, and its requirements are not restated here.",
"\"Incabloc\" is a registered trademark of Incabloc SA for one family of these devices, a trade name, not a generic word for the class. The company's own description names a \"pierced jewel\", an \"endstone\", a \"bushing\", a \"Lyre-spring®\" and a block, and states that the space between the pierced jewel and the endstone \"forms an 'oil sump' of optimised shape and size\". Those are the manufacturer's statements about its own product; the page carries no reference to ISO 1413, and its promotional wording is not repeated here as fact."
],
"related": [
"shock-resistance",
"jewel",
"balance-wheel",
"hairspring"
],
"sources": [
{
"tier": 1,
"citation": "ISO 1413:2016, Horology — Shock-resistant wrist watches, edition 3, published April 2016",
"url": "https://www.iso.org/standard/62753.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards, incl. NIHS 91-10 and NIHSG 42-01)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Incabloc SA, \"Shock absorbers\" (company product page)",
"url": "https://www.incabloc.ch/en/shock-absorbers/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Silicon hairspring",
"slug": "silicon-hairspring",
"aliases": [
"silicium hairspring",
"Si14",
"silicon balance spring"
],
"domain": "mechanism",
"status": "verified",
"short": "A balance spring etched from silicon rather than drawn from metal alloy, made to be non-magnetic and dimensionally stable.",
"full": [
"A silicon hairspring is a balance spring produced from a silicon wafer rather than drawn and coiled from a metal alloy. The published European patent application EP 3 056 948 A1, Silicon hairspring, in the name of Master Dynamic Limited of Hong Kong, was filed on 12 February 2016 and published on 17 August 2016. Its first claim covers a spring whose \"core formed from mono-crystalline silicon wafer oriented along the crystallographic axis <110>\" carries \"at least one peripheral coating of a material having a thermal elastic constant different from that of the core,\" the coating being how such a spring is made to compensate for temperature.",
"The application's own statement of what silicon offers over metal is that the material \"does not creep and oxidize over time in comparison with most metal alloys\", that it is \"entirely non-magnetic\", and that temperature sensitivity may be \"minimized or substantially eliminated for normal operating parameters\". These are assertions made in a patent application, a primary record of what was claimed, and when, not a measurement.",
"Omega markets its own silicon balance spring as the Si14, stating that \"In 2008, OMEGA released the Si14 balance spring, created to resist the ever-increasing magnetic forces that are part of our lives\", that it is \"Named after the chemical symbol and atomic number of silicon\", and that watches with its Co-Axial movement fitted with the Si14 \"are delivered with a full four-year warranty\". Those are Omega's own claims about its own product.",
"What is not established here: independent certification of the material itself. The Federation of the Swiss Watch Industry's published list of available NIHS norms contains no entry for silicium, and no standards body was found in this session that defines or tests a silicon balance spring as such. The claims quoted above stand as the applicant's and the brand's own words, not as figures from a neutral testing body."
],
"related": [
"hairspring",
"balance-wheel",
"magnetic-resistance",
"escapement"
],
"sources": [
{
"tier": 1,
"citation": "European Patent Office publication server, EP 3 056 948 A1, \"Silicon hairspring\", applicant Master Dynamic Limited, inventors Ching Ho Kowloon and Ko Pui Hang",
"url": "https://data.epo.org/publication-server/rest/v1.2/publication-dates/20160817/patents/EP3056948NWA1/document.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European Patent Office, Global Patent Index record for EP 3 056 948 A1, application EP 16155566, filed 12.02.2016, priority HK 15101776 of 17.02.2015, published 17.08.2016",
"url": "https://data.epo.org/gpi/EP3056948A1",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "OMEGA, Chronicle: \"2008 — OMEGA unveils the anti-magnetic silicon balance spring\"",
"url": "https://www.omegawatches.com/chronicle/2008-a-new-heart",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Fédération de l'industrie horlogère suisse FH, \"Liste des normes disponibles valable dès avril 2026\" (NIHS standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Detent escapement",
"slug": "detent-escapement",
"aliases": [
"chronometer escapement",
"spring detent escapement",
"pivoted detent"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "The marine chronometer's escapement, in which a detent holds the escape wheel and the balance takes one impulse per complete oscillation.",
"full": [
"The Seiko Museum Ginza calls it \"The detent escapement (chronometer escapement)\" and explains the name from the French: \"The French word détente means that something is not under pressure, and as the name implies, for the majority of the detent escapement's cycle, the balance can move freely.\" A detent locks the escape wheel; the balance trips it once per complete cycle and takes a single push, so that \"the balance encounters force from the escape wheel only once during the two swings of its cycle, its isochronism is maximized\", and with \"the pallet and the escape wheel being nearly parallel to each other, the friction was minimal\".",
"Who devised it is contested, and this Codex gives what each source says rather than choosing. The Seiko Museum Ginza credits the French clockmaker Pierre Le Roy in 1748. The Antiquarian Horological Society, a learned society rather than an issuing authority, lists under 1780 \"Thomas Earnshaw claims to have been working on a pivoted detent escapement\" and under 1782 \"John Arnold's patent for a spring detent escapement\". Royal Museums Greenwich, in its record for Earnshaw's portrait, states that Earnshaw \"devised the spring detent chronometer escapement and his own form of temperature-compensated chronometer balance in 1782,\" the same year the Society assigns to Arnold's patent.",
"The dispute was official in its own time. Royal Museums Greenwich holds a \"Model of Earnshaw's escapement\", commissioned by the Board of Longitude in 1804 so that the spring detent's action could be judged; its box is labelled \"Made by THOS. EARNSHAW in 1804 to the order of / The Board of Longitude.\" The museum records that a comparable model was made by John Roger Arnold, that both men were ultimately awarded £3,000, and that the argument over who invented the escapement has continued to the present day. The escapement's working life was long: the Seiko Museum Ginza states that \"Timepieces with detent escapements were used for standard time-keeping until quartz timepieces became the norm in the 1970s\"."
],
"related": [
"escapement",
"lever-escapement",
"chronometer",
"balance-wheel"
],
"sources": [
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Escapement for the Marine Chronometer\" (Knowledge: Mechanical Timepieces)",
"url": "https://museum.seiko.co.jp/en/knowledge/MechanicalTimepieces05/",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Antiquarian Horological Society, \"Historical timeline\"",
"url": "https://www.ahsoc.org/resources/historical-timeline/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, collection record \"Model of Earnshaw's escapement\"",
"url": "https://www.rmg.co.uk/collections/objects/rmgc-object-79228",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, collection record \"Thomas Earnshaw, 1749-1829\"",
"url": "https://www.rmg.co.uk/collections/objects/rmgc-object-14148",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Tourbillon",
"slug": "tourbillon",
"aliases": [
"tourbillon carriage",
"revolving carriage"
],
"domain": "mechanism",
"status": "verified",
"short": "A rotating carriage that carries a watch's escapement and balance, turning them continuously instead of letting them rest in one position.",
"full": [
"A tourbillon is a rotating cage, or carriage, in which the escapement and the balance of a watch are mounted, so that the oscillating parts are turned continuously rather than staying in whatever position the watch is held. The British Museum holds a pocket chronometer (museum number 1958,1201.1848) recorded as made by John Arnold in London in 1774, with the movement credited to Abraham Louis Breguet, who converted the watch in Paris between January 1808 and May 1809. The museum's curatorial comments record that Breguet \"added his newly invented revolving carriage, called a tourbillon, which constantly changed the position of the escapement and balance to minimize timekeeping errors caused by changes in the watch's position\".",
"Breguet's own archive dates the patent precisely. Its page is headed \"Patent granted for a completely new type of regulator called the 'Tourbillon'\" and gives the date as 26 June 1801, expressed in the French Republican calendar as 7 Messidor, year IX, with a term of ten years. The same page describes the construction as \"mounting the escapement assembly in a mobile cage that rotates on itself\" and the intention as \"designed to compensate for the operating errors and fluctuations caused by the effects of Earth's gravity\". Those are Breguet's own words about its own patent, and the page does not name the office that granted it.",
"What this Codex does not do: state a benefit. Neither source gives a figure for how much a tourbillon changes a watch's rate, and no test result is quoted on either page. The purpose above is the maker's stated intention and a museum's description of it, not a measured outcome."
],
"related": [
"escapement",
"balance-wheel",
"isochronism",
"complication"
],
"sources": [
{
"tier": 1,
"citation": "The British Museum, collection record: chronometer watch; box; tourbillon watch, museum number 1958,1201.1848 (John Arnold, London, 1774; tourbillon added by Abraham Louis Breguet, Paris, 1808-1809)",
"url": "https://www.britishmuseum.org/collection/object/H_1958-1201-1848",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Montres Breguet SA, corporate history, \"Patent granted for a completely new type of regulator called the 'Tourbillon'\" (Breguet's own archive account)",
"url": "https://www.breguet.com/en/breguet-house/1801-1823/patent-granted-completely-new-type-regulator-called-tourbillon",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Perpetual calendar",
"slug": "perpetual-calendar",
"aliases": [
"quantieme perpetuel"
],
"domain": "mechanism",
"status": "verified",
"short": "A calendar mechanism that carries the date through months of unequal length and through the four-year leap cycle without needing to be reset.",
"full": [
"A perpetual calendar is a date mechanism geared to the pattern of the Gregorian calendar rather than to a uniform 31-day month. Patek Philippe, describing its own calendar watches, says a perpetual calendar \"automatically takes into account monthly variations as well as leap years\", and that the firm built \"the first wristwatch equipped with a perpetual calendar back in 1925, based on a movement we produced in 1898\". That is Patek Philippe's own account of its own history.",
"The rule the mechanism has to follow comes from the calendar, not from the watch industry. The Astronomical Applications Department of the US Naval Observatory states it as follows: \"Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is.\"",
"Ordinary perpetual calendars implement only the first part of that rule. A patent application for a secular perpetual calendar, filed by Franck Mueller Watchland SA with Pierre-Michel Golay named as inventor (priority 14 February 2006), states that \"the correction made every four years by a conventional perpetual calendar is too great according to the Gregorian calendar\", because \"on each intermediate century, 2100, 2200, 2300 and 2500, 2600, 2700, etc., the leap year is eliminated\". The consequence follows arithmetically from the two sources: 2100 is divisible by four but not by 400, so a mechanism built on the four-year cycle alone will show 29 February 2100 and need correcting by hand."
],
"related": [
"annual-calendar",
"moon-phase",
"complication",
"leap-second"
],
"sources": [
{
"tier": 1,
"citation": "US Naval Observatory, Astronomical Applications Department, \"Introduction to Calendars\"",
"url": "https://aa.usno.navy.mil/faq/calendars",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Patek Philippe SA, \"Calendar watches\", Quality and fine workmanship (the company's own account)",
"url": "https://www.patek.com/en/manufacture/quality-and-fine-workmanship/calendar-watches",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "US patent application US 2007/0189122 A1, \"Secular Perpetual Calendar\", applicant Franck Mueller Watchland SA, inventor Pierre-Michel Golay, published 16 August 2007",
"url": "https://patents.google.com/patent/US20070189122A1/en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Annual calendar",
"slug": "annual-calendar",
"aliases": [
"quantieme annuel"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "A calendar mechanism that distinguishes 30-day from 31-day months but not leap years, so it needs one correction a year at the end of February.",
"full": [
"An annual calendar sits one step below a perpetual-calendar mechanism. Patek Philippe describes its own version in exactly those terms: \"It indicates the date for months of 30 and 31 days and needs only one correction per year, at the end of February.\" February is the one month such a mechanism cannot resolve, because it has 28 or 29 days while the wheel governing month length distinguishes only 30 from 31.",
"A European patent shows how the mechanism is arranged. EP 0 756 217 A1, \"Annual calendar mechanism for timepieces\", describes a date ring driven one step a day together with \"an annular crown wheel(8), partially superposed on the date ring(1), which rotates once a year\", carrying \"5 interior teeth(10) in positions corresponding to 31 day months\". At the end of a shorter month a second finger acts on one of those teeth and jumps the ring on to the first of the next month. The specification ends: \"A manual correction is required for the month of February.\"",
"The open question is who invented it. Patek Philippe's page says the annual calendar was \"invented and patented by Patek Philippe\" and introduced in 1996, but gives no patent number. The only annual-calendar patent of that period this Codex could retrieve and read, EP 0 756 217 A1, was filed on 15 July 1996 with a priority date of 28 July 1995 by Compagnie des Montres Longines Francillon SA, inventor Frank Vaucher. Patek Philippe's claim is recorded here as the company's claim about itself; its own patent has not been read, so the attribution is left unresolved."
],
"related": [
"perpetual-calendar",
"moon-phase",
"complication",
"dial"
],
"sources": [
{
"tier": 1,
"citation": "Patek Philippe SA, \"Calendar watches\", Quality and fine workmanship (the company's own account)",
"url": "https://www.patek.com/en/manufacture/quality-and-fine-workmanship/calendar-watches",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European patent application EP 0 756 217 A1, \"Annual calendar mechanism for timepieces\" (Mecanisme de quantieme annuel pour piece d'horlogerie), applicant Compagnie des Montres Longines Francillon SA, inventor Frank Vaucher, filed 15 July 1996, published 29 January 1997",
"url": "https://patents.google.com/patent/EP0756217A1/en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Moon phase",
"slug": "moon-phase",
"aliases": [
"moonphase",
"lunar phase"
],
"domain": "mechanism",
"status": "verified",
"short": "A display of the Moon's phase, driven by a wheel whose tooth count only approximates the 29.53-day mean interval between new moons.",
"full": [
"A moon-phase display shows how much of the Moon's disc is lit, advancing through the cycle from new moon to new moon. The interval it must follow is the synodic month. NASA's Goddard Space Flight Center states: \"The mean length of the synodic month is 29.53059 days (29d 12h 44m 03s).\" The same page gives the anomalistic month as 27.55455 days and the draconic month as 27.21222 days; it is the synodic figure that governs the visible phases.",
"The usual watch mechanism approximates that number with one toothed disc. A patent assigned to ETA SA Manufacture Horlogère Suisse describes the conventional arrangement as a moon-phase disc fitted with \"a star toothing 32, comprising 59 teeth\" advanced \"at a rate of one step per day\", which \"allows moon phase disc 18 to complete one revolution in 59 days, which equates to two lunations of 29.5 days\". The same patent sets out a variant in which the disc has \"135 teeth and completes one revolution in 59.0625 days, which equates to two lunations of 29.53125 days, very close to the true value\".",
"The drift is given here as arithmetic from those two figures, not as a quoted number. A 59-tooth wheel models the lunation as 29.5 days against a true mean of 29.53059, so the display gains about 0.0306 days — a little over 44 minutes — each lunation, and a full day of error accumulates after roughly 33 lunations, about two years and eight months. The 135-tooth variant cuts that to about 0.00066 days a lunation. Neither source says how often a wearer is expected to correct the display."
],
"related": [
"perpetual-calendar",
"annual-calendar",
"gear-train",
"complication"
],
"sources": [
{
"tier": 1,
"citation": "NASA Goddard Space Flight Center, \"Eclipses and the Moon's Orbit\", NASA eclipse web site",
"url": "https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "US patent US 7,649,811 B2, \"Timepiece with moon phase indicator\", assignee ETA SA Manufacture Horlogere Suisse",
"url": "https://patents.google.com/patent/US7649811B2/en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Minute repeater",
"slug": "minute-repeater",
"aliases": [
"minute repeating watch",
"repeater mechanism"
],
"domain": "mechanism",
"status": "verified",
"short": "A striking mechanism that sounds the time to the nearest minute only when the wearer operates it, instead of automatically at the hour.",
"full": [
"A minute repeater sounds the time on demand, in stages. The British Museum's record for a watch by Thomas Mudge of London, dated 1755 (museum number 1984,0301.1), describes a gilded-brass movement with \"separate trains for the quarter-striking and pendant-operated minute repeat mechanisms, both sounding on a bell\". The museum's curatorial comments explain that the repeating work is operated \"on demand to the nearest minute, simply by pushing in the watch pendant to activate the mechanism\", and that when activated it \"would strike a bell to sound the hour, the quarters past the hour and the minutes past the quarter\".",
"That is what separates a repeater from a striking clock or clock-watch, which sounds the hours whether or not anyone asks. The British Museum's record for a watch by Sir John Bennett of 1878–1880 (museum number 1980,0515.1) describes the object as a \"Minute-repeating, grande-sonnerie clock-watch\" — a single watch that does both — and notes of the two functions that \"the striking function must be completed before the watch can be made to repeat\". Automatic striking runs on its own; repeating happens only when a case control is pressed.",
"Both functions draw on stored energy rather than on the going train alone. The same British Museum record describes Hector Golay's arrangement in the Bennett watch, in which \"a single mainspring is used to power both the quarter- and hour-striking functions\". Neither record gives a figure for how much running time the striking work consumes, so no power-reserve cost is stated here."
],
"related": [
"complication",
"power-reserve",
"mainspring",
"gear-train"
],
"sources": [
{
"tier": 1,
"citation": "The British Museum, collection record: clock-watch; minute-repeating watch; quarter-striking watch, Thomas Mudge, London, 1755, museum number 1984,0301.1",
"url": "https://www.britishmuseum.org/collection/object/H_1984-0301-1",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The British Museum, collection record: minute-repeating watch; clock-watch, Sir John Bennett, 1878-1880, museum number 1980,0515.1",
"url": "https://www.britishmuseum.org/collection/object/H_1980-0515-1",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Dual time",
"slug": "dual-time",
"aliases": [
"GMT hand",
"second time zone"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "A function showing a second time zone beside local time, usually on an extra hand; the dial word GMT is trade usage, not the timescale.",
"full": [
"A dual-time watch shows two zones at once. Rolex, describing its own GMT-Master II, states: \"The GMT-Master II features an additional, triangle-tipped hand. This indicates a second time zone on the 24-hour graduated rotatable bezel.\" That is Rolex's own account of its own product, and note what the page does not do: it calls this the \"GMT function\" without anywhere defining the abbreviation or mentioning Greenwich Mean Time. No standard of ISO/TC 114, the ISO committee for horology, defines the dial term either: the eight it holds directly cover jewels, control-position symbols, wrist-chronometers, battery life, chemical compliance, hard-material external parts and watch batteries.",
"GMT as a timescale is a different thing from a second hour hand. Royal Museums Greenwich states that \"Greenwich Mean Time is the yearly average (or 'mean') of the time each day when the Sun crosses the Prime Meridian at the Royal Observatory Greenwich\", that \"from 1884 until 1972, GMT was the international standard of civil time\", and that \"though it has now been replaced by Coordinated Universal Time (UTC), GMT is still the legal time in Britain in the winter\". The timescale detail belongs to the entry for coordinated-universal-time.",
"The reference the zones are counted from is itself documented. Royal Museums Greenwich records that in 1884 delegates meeting in Washington \"voted to make the Greenwich Meridian the world's Prime Meridian\", and that \"the cross-hairs in the eyepiece of the Airy Transit Circle precisely defined zero degrees longitude for the world\". The museum's separate page \"What is the Prime Meridian, and why is it in Greenwich?\" adds that \"Earth's current internationally agreed prime meridian is the IERS Reference Meridian\", which \"passes 102.5 m to the east of the historic Prime Meridian\"."
],
"related": [
"world-time",
"coordinated-universal-time",
"bezel",
"complication"
],
"sources": [
{
"tier": 1,
"citation": "Royal Museums Greenwich, \"What is Greenwich Mean Time (GMT) - and why does it matter?\"",
"url": "https://www.rmg.co.uk/stories/time/greenwich-mean-time-gmt",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, \"What is the Prime Meridian, and why is it in Greenwich?\"",
"url": "https://www.rmg.co.uk/stories/time/what-prime-meridian-why-it-greenwich",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Rolex SA, \"GMT-Master II - One movement, two time zones\" (the company's own account)",
"url": "https://www.rolex.com/watches/gmt-master-ii/features",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO, ISO/TC 114 Horology, published standards catalogue (committee scope and the eight standards under the committee's direct responsibility)",
"url": "https://www.iso.org/committee/51734/x/catalogue/p/1/u/0/w/0/d/0",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "World time",
"slug": "world-time",
"aliases": [
"worldtimer",
"heures universelles"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "A display giving the time in every zone at once, read as a rotating 24-hour ring against a fixed ring of place names.",
"full": [
"A world-time display pairs a ring of place names, one for each time zone, with a rotating hour or 24-hour ring, so the time in any listed place can be read off directly. The British Museum holds an early example (museum number 1958,1201.907), a lever movement and dial of about 1860 described as a \"MOVEMENT AND DIAL OF A LEVER WATCH WITH WORLD TIME INDICATION\" with a \"rotating white enamel minute ring\" and a \"cream enamel outer ring with hours for 25 European cities\", GREENWICH set at XII. Its curatorial comments record that \"the dial design was patented in England by Modeste Anquetin on March 17th 1857\".",
"The reason one ring can work is that civil time is organised in zones counted from a single meridian. Royal Museums Greenwich records that at the 1884 conference in Washington delegates \"voted to make the Greenwich Meridian the world's Prime Meridian\" and \"also recommended a new global time zone system based on Greenwich Mean Time\". How many names a maker puts on the ring is its own choice, not a standard: the 1857 dial carries 25.",
"The open question is attribution. The modern world-time wristwatch layout is usually credited to the Geneva watchmaker Louis Cottier. This Codex could not verify that from the museum record it cites here: the British Museum record names Modeste Anquetin, Droz, Soldano and Beguelin, and not Cottier, and the accounts that do name him are enthusiast media, which this Codex does not cite. What is documented is that a dial of this kind was patented in England in 1857, some seventy years earlier."
],
"related": [
"dual-time",
"coordinated-universal-time",
"bezel",
"dial"
],
"sources": [
{
"tier": 1,
"citation": "The British Museum, collection record: world-time watch, movement by Soldano, dial design patented by Modeste Anquetin 1857, c.1860, museum number 1958,1201.907",
"url": "https://www.britishmuseum.org/collection/object/H_1958-1201-907",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Royal Museums Greenwich, \"What is the Prime Meridian, and why is it in Greenwich?\"",
"url": "https://www.rmg.co.uk/stories/time/what-prime-meridian-why-it-greenwich",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Hacking seconds",
"slug": "hacking-seconds",
"aliases": [
"stop-seconds",
"seconds hack",
"stop seconds"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "Trade term for a mechanism that stops the seconds hand when the crown is pulled out to set the time; no authority defines the term.",
"full": [
"The mechanism the trade calls hacking seconds is documented even though the name is not. US patent 3,765,164, \"Device to stop timepiece balance wheels\", assigned to Timex Corporation and filed on 11 January 1973, covers a spring that \"acts to bias a cock and also to selectively stop a balance wheel assembly\": pulling the stem out to the hand-setting position engages the lever's stop portion with the balance and halts its oscillation, so the watch is not running while the hands are moved. A patent assigned to Casio Computer Co. Ltd, US 4,636,087, does the same job further along the train, an arm being \"moved in the axial direction to engage with the top surface of gear 38 so as to stop its rotation\" when the crown is drawn out.",
"No authority defines the term. US 3,765,164 notes that \"This is sometimes called a hack feature\", but neither patent uses the words \"hacking\" or \"stop-seconds\", and neither states the purpose usually given for the feature — starting the watch against a reference signal so that it agrees to the second. ISO/TC 114, the ISO committee whose scope covers horological \"terminology; technical definitions\", lists eight standards under its own direct responsibility, on jewels, control-position symbols, wrist-chronometers, battery life, chemical regulatory compliance, hard-material external parts and watch batteries. None concerns this function.",
"This Codex also looked for a military procurement specification requiring the function, which would be a defensible near-miss. The United States Department of Defense specification for general-purpose wrist watches, MIL-PRF-46374, is the obvious candidate, but a search of the Department of Defense's own ASSIST QuickSearch catalogue at quicksearch.dla.mil returned no record for that number in this session, and no official copy of the text was retrieved. Third-party mirrors exist and were not used, so nothing is quoted from it here."
],
"related": [
"second",
"crown",
"keyless-works",
"balance-wheel"
],
"sources": [
{
"tier": 1,
"citation": "US patent US 3,765,164, \"Device to stop timepiece balance wheels\", assignee Timex Corporation, filed 11 January 1973, published 16 October 1973",
"url": "https://patents.google.com/patent/US3765164A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "US patent US 4,636,087, \"Gear train mechanism stop device of timepiece\", assignee Casio Computer Co. Ltd, filed 24 January 1986, published 13 January 1987",
"url": "https://patents.google.com/patent/US4636087A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO, ISO/TC 114 Horology, published standards catalogue (committee scope and the eight standards under the committee's direct responsibility)",
"url": "https://www.iso.org/committee/51734/x/catalogue/p/1/u/0/w/0/d/0",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Skeletonised",
"slug": "skeletonised",
"aliases": [
"skeleton watch",
"squelette"
],
"domain": "mechanism",
"status": "no-authoritative-definition",
"short": "A movement or dial whose plates have been cut away so the mechanism shows through; the British Museum catalogues such watches as skeletonised.",
"full": [
"Skeletonising means removing metal from the plates, bridges and sometimes the dial of a watch so that the mechanism behind them can be seen. The British Museum uses \"skeletonised watch\" as a catalogue object type. Its record for a watch signed \"H. DELOLME LONDON\" but recorded by the museum as Swiss-made, about 1900 (museum number 1958,1201.974), describes a \"three-quarter plate skeletonised movement, incorporating Royal Arms\" with a club-tooth lever escapement, and the curatorial notes the \"back plate pierced out including the Royal coat of arms\", carrying the motto \"DIEV ET MON DROIT\", with an engraved balance cock.",
"The work is not necessarily hand work, nor confined to the back. The museum's record for a watch by the New England Watch Company, 1912 (museum number 1958,1201.1381), reads \"Watch. Duplex escapement; skeletonised plates and dial. Metal-gilt dial. Nickel plated case; glazed both sides\", and the curatorial comments call it \"a less common type as it has a skeletonized movement and dial, which allows the mechanism to be seen from both sides through glasses at the front and back\". The same notes record that its parts were industrially made, \"some of them simply pressed from brass sheet\".",
"No authority defines the term. The British Museum applies the word to objects without defining it, and no threshold says how much metal must be removed before a movement counts as skeletonised. ISO/TC 114, the ISO committee for horology, holds eight standards directly — on jewels, control-position symbols, wrist-chronometers, battery life, chemical regulatory compliance, hard-material external parts and watch batteries — and none addresses decoration. The word is recorded here as museum cataloguing practice and trade usage, not as a specification."
],
"related": [
"dial",
"guilloche",
"watch-case",
"caseback"
],
"sources": [
{
"tier": 1,
"citation": "The British Museum, collection record: skeletonised watch, H. Delolme, London, c.1900, museum number 1958,1201.974",
"url": "https://www.britishmuseum.org/collection/object/H_1958-1201-974",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The British Museum, collection record: skeletonised watch; watch-case, New England Watch Company, 1912, museum number 1958,1201.1381",
"url": "https://www.britishmuseum.org/collection/object/H_1958-1201-1381",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO, ISO/TC 114 Horology, published standards catalogue (committee scope and the eight standards under the committee's direct responsibility)",
"url": "https://www.iso.org/committee/51734/x/catalogue/p/1/u/0/w/0/d/0",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Guilloché",
"slug": "guilloche",
"aliases": [
"guilloche",
"engine-turning",
"guillochage"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "A repeating pattern cut into metal on a rose engine lathe, by hand or by machine; no body certifies which method produced a given pattern.",
"full": [
"The Victoria and Albert Museum defines the word this way: \"Guilloché is a highly decorative technique used in metalwork, which combines mechanical engraving and translucent enamels to create surface embellishment.\" The museum dates its spread to the mid-eighteenth century: \"around the 1750s silversmiths began to use the rose engine lathe to cut metal surfaces with intricate patterns — such as waves and ripples, staggered lines, or sunburst rays — at an even depth and with unprecedented precision.\"",
"The machine survives in public collections. The Science Museum Group holds a rose engine lathe of about 1740 (object number 1912-53), recorded as able to \"cut shapes using a set of 'rosettes'\" and fitted with \"a cross slide rest which can move axially and radially\". The rosettes are the shaped cams that make the cutter rise and fall as the work turns, producing the repeating wave or ray pattern. The V&A notes that the lathe allowed \"delicate, intricate lines or precise geometric forms such as ellipses\" to be cut \"at a faster speed than engraving by hand\".",
"Watch usage is broader than the V&A's, because it applies the word to the engraved metal alone with no enamel over it. Breguet, describing its own dials, refers to \"hand turning the gold dials on rose engine\" and states that \"all of Breguet's guilloche dials, without exception, are created in this fashion respecting the finest hand craft traditions\", and that \"around 1786, Breguet began fitting his watches with engine-turned silver or gold dials of his own design\". Those are the company's statements about its own work.",
"The open question is certification. A pattern cut on a rose engine and one pressed or stamped into a dial can look similar, and this Codex found no body that certifies the difference. ISO/TC 114, the ISO committee for horology, holds eight standards directly, none of them concerning dial decoration or how it was produced. A claim that a dial is hand-guilloché rests on the maker's own statement."
],
"related": [
"dial",
"skeletonised",
"watch-case"
],
"sources": [
{
"tier": 1,
"citation": "Victoria and Albert Museum, \"How was it made? Guilloche enamelling\"",
"url": "https://www.vam.ac.uk/articles/how-was-it-made-guilloch%C3%A9-enamelling",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Science Museum Group Collection, object record: Rose engine lathe, c.1740, object number 1912-53",
"url": "https://collection.sciencemuseumgroup.org.uk/objects/co46302/rose-engine-lathe-lathe-machine",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Montres Breguet SA, \"Guillochage\" (the company's own account of its own dials)",
"url": "https://www.breguet.com/en/guillochage",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO, ISO/TC 114 Horology, published standards catalogue (committee scope and the eight standards under the committee's direct responsibility)",
"url": "https://www.iso.org/committee/51734/x/catalogue/p/1/u/0/w/0/d/0",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Mechanical watch",
"slug": "mechanical-watch",
"aliases": [
"mechanical movement"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "A watch powered by a wound spring and regulated by a moving mechanical oscillator, with no battery in the timekeeping path.",
"full": [
"A mechanical watch takes all of its energy from a wound metal spring and regulates its release with a moving mechanical oscillator. Grand Seiko's own technical page sets out the chain: \"A wound-up mainspring exerts force to turn gears at a set speed as it unwinds\", and \"the escapement regulates the rotation of the gears to ensure precise timekeeping\".",
"The spring can be wound by hand or by the wearer's movement, and one movement can accept both. A patent filed by Montres Breguet SA on 21 June 2022, \"Device for automatic winding of a barrel spring of a timepiece movement\", describes winding by an \"oscillating mass\" that \"drives the first wheel to rotate\", while also retaining stem winding.",
"The craft, rather than the object, carries a heritage listing. The Swiss Commission for UNESCO states: \"Le 16 décembre 2020 l'UNESCO a inscrit les savoir-faire en mécanique horlogère et mécanique d'art sur la Liste représentative du patrimoine culturel immatériel de l'humanité.\" It was a joint Swiss and French nomination. The Musée international d'horlogerie gives the English form: \"UNESCO has registered the craftsmanship of mechanical watchmaking and art mechanics on its Representative List of the Intangible Cultural Heritage of Humanity.\" UNESCO's own committee decision, 15.COM 8.B.8 on nomination file 01560, submitted by Switzerland and France, \"Decides to inscribe Craftsmanship of mechanical watchmaking and art mechanics on the Representative List of the Intangible Cultural Heritage of Humanity\".",
"What this Codex does not do: quote UNESCO's element page. That page still refuses requests from this environment, so the decision text above is cited instead; it carries the operative wording and the file number, and the 16 December 2020 date comes from the two national sources. No standards body's definition of \"mechanical watch\" was read at all, so the category is described above from a manufacturer's page and a granted patent, not a standard."
],
"related": [
"automatic",
"hand-winding",
"mainspring",
"quartz-movement"
],
"sources": [
{
"tier": 1,
"citation": "Grand Seiko, \"Mechanical\" movement page (company technical page)",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European Patent Office, EP 4 296 788 B1, Montres Breguet SA, \"Device for automatic winding of a barrel spring of a timepiece movement\", filed 21 June 2022 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/EP4296788B1/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Commission for UNESCO, \"Les savoir-faire en mécanique horlogère et mécanique d'art inscrits à l'UNESCO\"",
"url": "https://www.unesco.ch/les-savoir-faire-en-mecanique-horlogere-et-mecanique-dart-inscrits-a-lunesco/?lang=en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "UNESCO, \"Decision of the Intergovernmental Committee: 15.COM 8.B.8\" (Intangible Cultural Heritage Committee decision)",
"url": "https://ich.unesco.org/en/decisions/15.COM/8.B.8",
"accessed": "2026-09-27"
},
{
"tier": 1,
"citation": "Musée international d'horlogerie, La Chaux-de-Fonds, \"UNESCO Heritage\"",
"url": "https://www.mih.ch/en/unesco-heritage/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-27",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Hand-winding",
"slug": "hand-winding",
"aliases": [
"manual winding",
"manual-wind",
"hand-wound"
],
"domain": "mechanism",
"status": "verified",
"short": "Winding a watch's mainspring by turning the crown, which drives the keyless works instead of a separate winding key.",
"full": [
"Hand-winding is the transfer of energy into the mainspring by turning the crown. The crown sits on a stem, and the stem drives the keyless works. A patent assigned to Ebauches Bettlach SA, \"Winding and setting mechanism for watches\" (US 3,827,235, filed 18 June 1973), describes a drive pinion \"rigidly connected with the stem\" and a \"sliding crown wheel\" \"cooperating with the ratchet wheel for the winding of the drive spring\". Pushed in, the stem winds the spring; pulled out, the same pinion meshes with the setting wheel and the hands move instead.",
"The arrangement is old. Christopher Kuenzel's US patent 739,089, \"Stem winding and setting watch\", published 15 September 1903, describes a stem whose \"outward movement\" \"insures the forcing of the clutch out of winding engagement with the barrel and the setting-pinion into setting engagement with the hand-setting train of gearing,\" one crown doing two jobs, which is still how a hand-wound watch behaves.",
"What winding achieves is stored torque. Grand Seiko's technical page states that \"a wound-up mainspring exerts force to turn gears at a set speed as it unwinds\". Hand-winding is not confined to watches without a rotor: Montres Breguet's 2022 automatic-winding patent describes a movement wound both by an oscillating mass and, still, through the winding stem.",
"\"Hand-winding\" is trade vocabulary rather than a defined technical term. The primary documents cited here call the assembly a \"winding and setting mechanism\", and no standards body, metrology institute or museum record read for this entry defines the phrase itself."
],
"related": [
"crown",
"keyless-works",
"mainspring",
"automatic"
],
"sources": [
{
"tier": 1,
"citation": "United States Patent Office, US 3,827,235, Ebauches Bettlach SA (inventor P. Bachmann), \"Winding and setting mechanism for watches\", filed 18 June 1973, published 6 August 1974 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US3827235A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "United States Patent Office, US 739,089, Christopher Kuenzel, \"Stem winding and setting watch\", filed 10 March 1903, published 15 September 1903 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US739089A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Grand Seiko, \"Mechanical\" movement page (company technical page)",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European Patent Office, EP 4 296 788 B1, Montres Breguet SA, \"Device for automatic winding of a barrel spring of a timepiece movement\", filed 21 June 2022 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/EP4296788B1/en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Rotor",
"slug": "rotor",
"aliases": [
"oscillating weight",
"winding rotor",
"oscillating mass"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "The pivoted weight inside a self-winding watch that turns with the wearer's movement and winds the mainspring.",
"full": [
"A rotor is a weighted mass pivoted inside the movement so that ordinary arm movement turns it, and that turning winds the mainspring. The category it creates is covered in this Codex under automatic. John Harwood and H. Cutts's British patent GB 218,487, \"Improvements relating to wrist watches\", filed 7 July 1923 and published 10 July 1924, describes \"watches wound automatically by a weight oscillated by the movement of the wearer\", in which \"overwinding is prevented by frictionally connecting the weight A to a plate D pivoted on the same spindle\".",
"Harwood's US patent 1,576,120, \"Wrist watch and other watch\", filed 8 October 1923 and granted 9 March 1926, is more explicit: \"the winding of the main spring is effected by an oscillating weight pivoted within the watch, the oscillation of this weight when the watch is being worn turning a plate or member frictionally connected to the weight\".",
"The patent vocabulary has not changed in a century. Montres Breguet SA's EP 4 296 788 B1, filed 21 June 2022, is still written around an \"oscillating mass\" that \"drives the first wheel to rotate\"; the word \"rotor\" does not appear in it. No standards body or metrology institute read for this entry defines the word.",
"What this Codex does not do: repeat the customary attributions without a record. The claim that Abraham-Louis Perrelet built a self-winding mechanism in the 1770s is widely circulated, but no museum or archive record confirming it was retrieved for this entry, so it is not stated here as fact."
],
"related": [
"automatic",
"mainspring",
"barrel",
"power-reserve"
],
"sources": [
{
"tier": 1,
"citation": "UK Patent Office, GB 218,487 A, J. Harwood and H. Cutts, \"Improvements relating to wrist watches\", filed 7 July 1923, published 10 July 1924 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/GB218487A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "United States Patent Office, US 1,576,120, John Harwood, \"Wrist watch and other watch\", filed 8 October 1923, granted 9 March 1926 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US1576120A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "European Patent Office, EP 4 296 788 B1, Montres Breguet SA, \"Device for automatic winding of a barrel spring of a timepiece movement\", filed 21 June 2022 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/EP4296788B1/en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Barrel",
"slug": "barrel",
"aliases": [
"mainspring barrel",
"barrel drum"
],
"domain": "mechanism",
"status": "verified",
"short": "The toothed drum that houses a watch's coiled mainspring and delivers its torque to the gear train as the spring unwinds.",
"full": [
"A barrel is an energy-storage assembly: a toothed drum with a cover, a central arbor, and a coiled mainspring hooked between the two. A patent assigned to ETA SA Manufacture Horlogère Suisse, \"Timepiece barrel\" (US 9,367,037 B2, priority 18 December 2012), places it in \"the field of timepiece mechanisms, and more specifically energy storage mechanisms, of the mainspring barrel, striking barrel or similar type\", and describes the spring as \"hooked between said drum at the outer end thereof and an arbor at the inner end thereof\", with the arbor \"pivotally integral with a ratchet about a pivot axis\".",
"A Seiko Epson patent, \"Spring, mainspring, hairspring, and driving mechanism and timepiece based thereon\" (US 6,863,435 B2, published 8 March 2005), states the function in one line: a timepiece driving mechanism \"comprises a mainspring serving as a power source, a barrel drum housing the mainspring, and a train wheel transmitting a mechanical energy of the mainspring by engaging with the barrel drum\". The drum's own teeth are therefore where the going train begins.",
"Because a spring pushes hardest when fully wound and weakest as it runs down, the barrel is where a movement's torque curve starts. Grand Seiko's technical page describes the intended behaviour as the mainspring unwinding \"gradually and evenly over a long period of time\", that motion being \"transmitted through the gear train\". How long it lasts is the watch's power reserve."
],
"related": [
"mainspring",
"gear-train",
"power-reserve",
"keyless-works"
],
"sources": [
{
"tier": 1,
"citation": "United States Patent and Trademark Office, US 9,367,037 B2, ETA SA Manufacture Horlogère Suisse, \"Timepiece barrel\", priority 18 December 2012, published 14 June 2016 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US9367037B2/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "United States Patent and Trademark Office, US 6,863,435 B2, Seiko Epson Corporation, \"Spring, mainspring, hairspring, and driving mechanism and timepiece based thereon\", published 8 March 2005 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US6863435B2/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Grand Seiko, \"Mechanical\" movement page (company technical page)",
"url": "https://www.grand-seiko.com/us-en/collections/movement/mechanical",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Keyless works",
"slug": "keyless-works",
"aliases": [
"keyless work",
"winding and setting mechanism",
"stem winding"
],
"domain": "mechanism",
"status": "verified",
"short": "The crown-and-stem mechanism that both winds a watch and sets its hands, replacing the detachable key earlier watches needed.",
"full": [
"The keyless works is the train of wheels, pinions and levers between the crown and the movement, and it does two jobs with one control. A patent assigned to Ebauches Bettlach SA, \"Winding and setting mechanism for watches\" (US 3,827,235, filed 18 June 1973), describes a drive pinion \"rigidly connected with the stem\", a \"sliding crown wheel\" \"cooperating with the ratchet wheel for the winding of the drive spring\", and a setting wheel between the drive pinion and the periphery of the movement, coupled to the time indicating means. The stem's axial position decides which of the two the pinion engages.",
"Christopher Kuenzel's US patent 739,089, \"Stem winding and setting watch\" (published 15 September 1903), describes the same switch in period language: a two-part stem in which \"an outward movement of one of the sections insures the forcing of the clutch out of winding engagement with the barrel and the setting-pinion into setting engagement with the hand-setting train of gearing\".",
"Before this existed, a watch was wound and set with a detachable key. The Science Museum Group's record for a \"Pocket Watch with Keyless Winding by Payne & Co, 1845-1855\" describes a \"Swiss watch, with unusual form of keyless winding mechanism\", placing working keyless watches in the mid-nineteenth century. Patek Philippe's own account of its founders states of Adrien Philippe that \"in 1842, he invented the keyless mechanism that attracted Patek's attention\".",
"What this Codex does not do: name a first. The Science Museum record claims no priority, and Patek Philippe's date of 1842 is the company's own account of its own founder. The patents cited here are primary documents for the mechanism, not for who built one first."
],
"related": [
"crown",
"hand-winding",
"mainspring",
"barrel"
],
"sources": [
{
"tier": 1,
"citation": "United States Patent Office, US 3,827,235, Ebauches Bettlach SA (inventor P. Bachmann), \"Winding and setting mechanism for watches\", filed 18 June 1973 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US3827235A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "United States Patent Office, US 739,089, Christopher Kuenzel, \"Stem winding and setting watch\", published 15 September 1903 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US739089A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Science Museum Group Collection, object co558, \"Pocket Watch with Keyless Winding by Payne & Co, 1845-1855\"",
"url": "https://collection.sciencemuseumgroup.org.uk/objects/co558/pocket-watch-with-keyless-winding-by-payne-co-1845-1855",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Patek Philippe, \"The Story of the Founding of Patek Philippe — The founders\" (company heritage page)",
"url": "https://www.patek.com/en/manufacture/a-story-of-independence/the-founders",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Eco-Drive",
"slug": "eco-drive",
"aliases": [
"Eco Drive",
"light-powered quartz"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "Citizen's own name for its light-powered quartz watches, which store converted light energy in a rechargeable cell rather than a battery.",
"full": [
"Eco-Drive is Citizen's own name for its light-powered quartz watches, not a generic description of solar watches. Citizen states that \"Eco-Drive is a proprietary CITIZEN technology that converts any kind of light, from bright sunshine to dim indoor lighting, into the energy necessary to power a watch\". The energy is held in a secondary, rechargeable cell (Citizen's page names \"a lithium secondary battery\") and Citizen states that \"Eco-Drive makes regular battery replacement unnecessary\".",
"Every performance figure attached to Eco-Drive is Citizen's own stated figure. Citizen states that an Eco-Drive watch \"runs for over six months off a single full charge\", and its support pages put this as continuing \"even in total darkness\". Citizen further states that \"there are now several Eco-Drive models with power save function that have a running time of seven years\". No independent testing body publishes a rating for any of these numbers, and none was found for this entry.",
"Citizen dates the technology to its own earlier work: \"in 1976, we invented the world's first light-powered analog quartz watch that runs using only light as a power source.\" That priority is not only Citizen's claim: the Seiko Museum separately records that \"in 1976, Citizen launched the Crystron Solar Cell, the world's first analog solar-powered watch\".",
"What this Codex does not do: cite a trademark register. Eco-Drive is treated here as Citizen's mark because Citizen describes it on its own site as \"proprietary CITIZEN technology\"; no register entry at WIPO, EUIPO or the USPTO was opened from this session, so no registration number or jurisdiction is stated."
],
"related": [
"quartz-movement",
"thermocompensated-quartz",
"power-reserve",
"radio-controlled-watch"
],
"sources": [
{
"tier": 1,
"citation": "Citizen Watch Co., \"Eco-Drive | CITIZEN Technologies\" (company technical page)",
"url": "https://www.citizenwatch-global.com/technologies/eco-drive/index.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Citizen Watch US, \"What is Eco-Drive?\" (company support page)",
"url": "https://support.citizenwatch.com/hc/en-us/articles/360007744914-What-is-Eco-Drive",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Alternative power sources for quartz watches\"",
"url": "https://museum.seiko.co.jp/en/knowledge/Quartz05/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Spring Drive",
"slug": "spring-drive",
"aliases": [
"tri-synchro regulator",
"glide wheel"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "Seiko's own name for a movement powered only by a mainspring but regulated electronically by a quartz oscillator instead of an escapement.",
"full": [
"Spring Drive is Seiko's name for a movement whose only power source is a wound mainspring, but whose rate is set electronically rather than by an escapement. Seiko Epson's patent application \"Electronically controlled mechanical timepiece\" (EP 0 905 587 A1, priority 26 September 1997) describes it: a generator is driven by rotation received from the train wheel, and \"the rotation cycle of the generator is controlled in response to a control signal\". The circuit contains \"a quartz oscillator\" producing \"a reference frequency signal\", against which the detected rotation is compared before the generator is braked electromagnetically.",
"Seiko's own product pages call the arrangement the tri-synchro regulator, which \"controls the mainspring's mechanical energy\", \"converts a small part of this energy into electricity\" and \"generates a magnetic force to regulate the speed of the glide wheel\". There is no escapement and no balance wheel: the glide wheel turns continuously against an electromagnetic brake, which is why the seconds hand sweeps rather than steps. The mainspring supplies all the energy; the electronics only decide how fast it may be spent.",
"The accuracy figures are Seiko's own claims. The Seiko Museum dates the first model to 1999 (\"the world's first watch driven by the mainspring power and controlled by quartz at the same time\") and describes \"high precision comparable to that of a quartz watch (e.g., a monthly difference rate of less than ±15 seconds)\". Seiko's product-knowledge page instead states \"one-second-a-day accuracy\", with a 72-hour power reserve. Both are Seiko statements about Seiko products; they are not reconciled on either page, and no independent body publishes a rating for Spring Drive."
],
"related": [
"quartz-movement",
"mainspring",
"escapement",
"power-reserve"
],
"sources": [
{
"tier": 1,
"citation": "European Patent Office, EP 0 905 587 A1, Seiko Epson Corporation, \"Electronically controlled mechanical timepiece\", priority 26 September 1997, published 31 March 1999 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/EP0905587A1/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "The Seiko Museum Ginza, \"Spring Drive\" (Seiko Milestones)",
"url": "https://museum.seiko.co.jp/en/seiko_history/milestone/a6946f3e0078a97d44d08dd303293ba0d8ca8430/",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Seiko Watch Corporation, \"Spring Drive\" (company product-knowledge page)",
"url": "https://www.seikowatches.com/us-en/customerservice/knowledge/springdrive-knowledge",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Tuning-fork watch",
"slug": "tuning-fork-watch",
"aliases": [
"Accutron",
"Bulova Accutron"
],
"domain": "mechanism",
"status": "verified",
"short": "A watch whose oscillator is an electromagnetically driven tuning fork rather than a balance wheel; Bulova's Accutron is the known example.",
"full": [
"In a tuning-fork watch the timekeeping oscillator is a small metal fork kept vibrating by electromagnets and a transistor circuit, its vibration converted into rotary motion to drive the hands. Max Hetzel's US patent 2,900,786, \"Timepiece arrangement\", assigned to Bulova Watch Company, Inc., filed 31 May 1956 and granted 25 August 1959, describes \"an arrangement of an electric timepiece incorporating a vibrator for driving the timepiece mechanism\", built around a \"tuning-fork type vibrator having a base and a pair of oscillatable tines\".",
"The dates and figures usually quoted for the Accutron are the company's own. An Accutron press release states that \"65 years ago, on October 25th, Accutron changed the industry with the original Tuning Fork movement\", calls it the \"first electronic wristwatch, achieving unheard-of accuracy within 2 seconds per day\", and says that \"the 360 Hz vibration required precision tolerances that demanded completely new micro-engineering processes\". All three figures are the brand's own statements about itself.",
"Use of the movement beyond wristwatches is on the public museum record. The Smithsonian National Air and Space Museum's record for a Skylab timer made by Bulova Watch Company (inventory A19761052000) states that \"timers like this were used by astronauts to time experiments and other events during the Skylab missions (1973-1974)\", and that it uses \"the 'Accutron' movement developed by Bulova for wristwatches\". The National Museum of American History holds a military Accutron wristwatch of about 1970, catalogue 1993.0254.09.",
"What this Codex does not do: extend that record to other programmes. The Air and Space Museum record names Skylab; the wider claim on Bulova's own pages that the timing device \"was adopted for the Apollo program\" was not verified against a museum or NASA record."
],
"related": [
"quartz-movement",
"balance-wheel",
"hertz",
"escapement"
],
"sources": [
{
"tier": 1,
"citation": "United States Patent Office, US 2,900,786, Max Hetzel (assignee Bulova Watch Company, Inc.), \"Timepiece arrangement\", filed 31 May 1956, granted 25 August 1959 (read via Google Patents' copy)",
"url": "https://patents.google.com/patent/US2900786A/en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Accutron, press release \"Accutron brings back the hum: the tuning fork watch returns to history\" (company press release)",
"url": "https://www.prnewswire.com/news-releases/accutron-brings-back-the-hum-the-tuning-fork-watch-returns-to-history-302599974.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Smithsonian National Air and Space Museum, collection record \"Timer, Skylab\", inventory A19761052000",
"url": "https://airandspace.si.edu/collection-objects/timer-skylab/nasm_A19761052000",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Smithsonian National Museum of American History, collection record \"wristwatch, military bulova accutron\", catalogue 1993.0254.09",
"url": "https://americanhistory.si.edu/collections/search/object/nmah_1161057",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Radio-controlled watch",
"slug": "radio-controlled-watch",
"aliases": [
"radio-synchronised watch",
"radio-controlled clock",
"atomic timekeeping watch"
],
"domain": "mechanism",
"status": "verified",
"short": "A quartz watch with a radio receiver that periodically resets itself from a national time-signal broadcast and keeps its own time in between.",
"full": [
"A radio-controlled watch is an ordinary quartz watch with a receiver added. NIST, describing radio-controlled clocks that use its station WWVB, explains that the device has \"a miniature radio receiver inside, which is permanently tuned to receive the 60 kHz signal\", and that the broadcast sends bits at \"1 bit per second, and it takes a full minute to send a complete time code\". The watch decodes that code and resets its display.",
"The signals are national metrology broadcasts, not a service of the watch industry. Germany's Physikalisch-Technische Bundesanstalt transmits DCF77 on a 77.5 kHz carrier from Mainflingen, to \"disseminate the legal time realized by PTB for Germany\". The United Kingdom's MSF, in the National Physical Laboratory's words, \"operates on a frequency of 60 kHz\" and is \"transmitted from Anthorn Radio Station in Cumbria\". Japan's NICT broadcasts under the \"call sign JJY\" on \"40 kHz\" and \"60 kHz\" from its Ohtakadoyayama and Haganeyama stations.",
"A radio-controlled watch is therefore only as good as its last successful reception. NIST states that \"most clocks only decode the signal once per day, but some do it more often (for example, every 6 hours)\", usually \"at midnight or in the very early hours of the morning, because the signal is easiest to receive when it is dark\", and that \"in between synchronizations, the clocks keep time using their quartz crystal oscillators\".",
"The time carried by these signals comes from the atomic clocks the institutes operate, not from anything inside the watch: \"atomic watch\" describes where the time came from rather than what the watch is. NICT publishes an \"accuracy of frequency and time interval\" for JJY of \"+-1*10-12\"; the watch inherits none of that between receptions."
],
"related": [
"atomic-clock",
"quartz-movement",
"coordinated-universal-time",
"second"
],
"sources": [
{
"tier": 1,
"citation": "NIST, \"Help with WWVB Radio Controlled Clocks\", Time and Frequency Division",
"url": "https://www.nist.gov/pml/time-and-frequency-division/time-distribution/radio-station-wwvb/help-wwvb-radio-controlled",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Physikalisch-Technische Bundesanstalt, \"DCF77\", Dissemination of Legal Time",
"url": "https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "National Physical Laboratory (UK), \"MSF signal\"",
"url": "https://www.npl.co.uk/msf-signal",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "National Institute of Information and Communications Technology (Japan), standard time and frequency signal transmission, JJY",
"url": "https://jjy.nict.go.jp/jjy/trans/index-e.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Thermocompensated quartz",
"slug": "thermocompensated-quartz",
"aliases": [
"high-accuracy quartz",
"HAQ",
"thermocompensation",
"temperature-compensated crystal oscillator"
],
"domain": "mechanism",
"status": "verified-with-open-question",
"short": "A quartz movement that measures its own temperature and corrects the frequency error that temperature causes in the crystal.",
"full": [
"A quartz crystal's frequency is not fixed. NIST's account of frequency measurement states that, of the influences on a crystal oscillator, \"temperature changes are the largest problem, but other parameters such as humidity, pressure, and vibration can also change the frequency\". An ordinary watch crystal is trimmed to run correctly near one temperature, so a wrist warmer or colder than that shifts the rate.",
"Compensation does not prevent the shift; it measures it and subtracts it. NIST describes the standard method: \"an alternative solution to the temperature problem is the temperature-compensated crystal oscillator (TCXO). These devices include a temperature sensor that generates a correction voltage that is applied to a voltage-variable reactance, or varactor.\"",
"The published watch figures are the brands' own. Grand Seiko states of its 9F quartz that \"the temperature inside the watch is also measured 540 times a day\", giving a stated \"±10 seconds per year\", and that its oscillators are \"'aged' for three months\" before selection. Citizen states: \"we have achieved the highest levels of annual accuracy: ±5 seconds and ±1 second\", with the internal temperature monitored \"once per minute for a total of 1,440 measurements per day\". These are company statements about company products.",
"On independent rating: COSC does test quartz (its FAQ states that its certification \"attests to the high precision of the movement, whether this is mechanical or quartz\") but the same page publishes numerical limits only for mechanical watches, saying of quartz merely that \"quartz movements follow internal requirements inspired by this standard but adapted to their specific features\". None of the figures above corresponds to a limit certified by a neutral body."
],
"related": [
"quartz-movement",
"chronometer",
"daily-rate",
"eco-drive"
],
"sources": [
{
"tier": 1,
"citation": "NIST, Michael A. Lombardi, \"Frequency Measurement\" (chapter 42), hosted by the NIST Time and Frequency Division",
"url": "https://tf.nist.gov/general/pdf/2496.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Grand Seiko, \"Quartz\" movement page (company technical page)",
"url": "https://www.grand-seiko.com/us-en/collections/movement/quartz",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Citizen Watch Co., \"Next Level Precision\", The CITIZEN official site (company technical page)",
"url": "https://www.citizenwatch-global.com/the-citizen/philosophy/precision.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "COSC (Contrôle Officiel Suisse des Chronomètres), \"COSC FAQ: All your questions answered\"",
"url": "https://www.cosc.swiss/cosc-faq",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Swiss made",
"slug": "swiss-made",
"aliases": [
"Swiss Made",
"Swiss movement"
],
"domain": "trade",
"status": "verified",
"short": "A legally defined origin mark for watches, set by a Swiss federal ordinance that fixes where the development, movement, casing and costs must originate.",
"full": [
"\"Swiss made\" is a condition of Swiss federal law, not a marketing phrase. The instrument is the Ordinance of 23 December 1971 on the Use of the Designation \"Swiss\" for Watches, carried in the Swiss classified compilation as SR 232.119. The Swiss Federal Institute of Intellectual Property states that \"The revised 'Swiss Made' Ordinance for Watches entered into force on 1 January 2017\".",
"Article 1a sets out when a watch is Swiss. In the text reproduced by the Federation of the Swiss Watch Industry FH, the conditions are that \"its technical development has taken place in Switzerland\"; that \"its movement is Swiss\"; that \"its movement has been cased up in Switzerland\"; that \"final inspection by the manufacturer took place in Switzerland\"; and that \"at least 60% of the manufacturing costs is generated in Switzerland\". The Institute puts the cost condition as \"At least 60 per cent of the costs of manufacturing a complete watch (as an end product) must be generated in Switzerland\".",
"Article 2 applies a second, separate test to the movement: it must \"have undergone technical development in Switzerland\", \"have been assembled in Switzerland\", and \"have been inspected by the manufacturer in Switzerland and at least 60% of the manufacturing costs must be generated in Switzerland and at least 50% of the value of all the constituent parts, but excluding the cost of assembly, must be of Swiss manufacture\". FH records that the 2017 revision raised the movement's threshold to \"a minimum rate of Swiss value of 60% (as opposed to the previous 50%)\".",
"Two precisions. The ordinance dates from 1971; its revised version entered into force on 1 January 2017. And Article 2c removes several items from the cost calculation, among them packaging, transport, marketing and customer-service costs, and the cost of the battery."
],
"related": [
"geographical-indication",
"in-house-movement",
"manufacture",
"counterfeit"
],
"sources": [
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Guide to the use of the designation 'Swiss' for watches\", version 5, reproducing the Ordinance of 23 December 1971",
"url": "https://www.fhs.swiss/file/8/Guide_FH_v.5_en.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Federal Institute of Intellectual Property (IPI), \"Revision of the Ordinance on the Use of 'Swiss' for Watches\"",
"url": "https://www.ige.ch/en/law-and-policy/national-ip-law/indications-of-source/swiss-indications-of-source/industry-ordinances/revision-of-the-ordinance-on-the-use-of-swiss-for-watches",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "WIPO Lex, \"Ordinance of December 23, 1971, on the Use of the Designation 'Swiss' for Watches\", Switzerland, SR 232.119",
"url": "https://www.wipo.int/wipolex/en/legislation/details/19179",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"The criteria for strengthening the Swiss made label\"",
"url": "https://www.fhs.swiss/eng/strengthening.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Geographical indication",
"slug": "geographical-indication",
"aliases": [
"geographical indications",
"appellation of origin",
"indication of source"
],
"domain": "trade",
"status": "verified",
"short": "A sign used on products that have a specific geographical origin and possess qualities or a reputation due to that origin.",
"full": [
"The World Intellectual Property Organization states the definition plainly: \"A geographical indication (GI) is a sign used on products that have a specific geographical origin and possess qualities or a reputation that are due to that origin.\" WIPO lists four main ways such signs are protected: \"so-called sui generis systems (i.e. special regimes of protection)\"; collective or certification marks; \"methods focusing on business practices, including administrative product approval schemes\"; and unfair competition laws.",
"The treaty wording is narrower. The United States Patent and Trademark Office quotes Article 22(1) of the WTO TRIPS Agreement, covering \"indications which identify a good as originating in the territory of a Member, or a region or locality in that territory, where a given quality, reputation or other characteristic of the good is essentially attributable to its geographic origin\". The USPTO explains that the United States protects such indications through its ordinary trade mark system, \"usually as certification and collective marks\".",
"Watchmaking has two examples that can be read in the law itself. \"Swiss\" for watches is governed by a dedicated industry ordinance; the Swiss Federal Institute of Intellectual Property records that such sector ordinances exist for watches and cosmetics only. \"Glashütte\" is governed in Germany by the Regulation on the Protection of the Name Glashütte (GlashütteV) of 22 February 2022, issued under Section 137 of the German Trade Mark Act. German customs states the name may be used only where \"more than 50 per cent of the value creation is achieved in the area of origin\", with assembly, adjustment and encasing carried out in Glashütte itself.",
"What this Codex does not claim: that Geneva is protected in the same way. No instrument establishing \"Genève\" as an indication of source for watches was located and read for this entry, so none is described here."
],
"related": [
"swiss-made",
"hallmark",
"counterfeit",
"poincon-de-geneve"
],
"sources": [
{
"tier": 1,
"citation": "World Intellectual Property Organization, \"Geographical Indications\"",
"url": "https://www.wipo.int/web/geographical-indications",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "United States Patent and Trademark Office, \"Geographical Indication Protection in the United States\"",
"url": "https://www.uspto.gov/sites/default/files/web/offices/dcom/olia/globalip/pdf/gi_system.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "German Customs Administration (Zoll), \"Glashütte Regulation\", Regulation on the Protection of the Name Glashütte (GlashütteV) of 22 February 2022",
"url": "https://www.zoll.de/EN/Businesses/Movement-of-goods/Import/Restrictions/Goods/Protection-of-industrial-property/Indications-of-geographical-source/Protected-rights/National-legislation/Glashuette-Regualtion/glashuette-regualtion_node.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Federal Institute of Intellectual Property (IPI), \"Industry ordinances\" (Swiss indications of source)",
"url": "https://www.ige.ch/en/law-and-policy/national-ip-law/indications-of-source/swiss-indications-of-source/industry-ordinances",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Hallmark",
"slug": "hallmark",
"aliases": [
"hallmarking",
"assay mark",
"Common Control Mark"
],
"domain": "trade",
"status": "verified",
"short": "A mark struck on an article of precious metal by an official body to record the proportion of precious metal it contains.",
"full": [
"India's Bureau of Indian Standards gives a definition that fits every national system: \"Hallmarking is the accurate determination and official recording of the proportionate content of precious metal in precious metal articles.\" The reason it is compulsory appears in the UK government's hallmarking guidance: \"It is not possible to detect by sight or by touch the platinum, gold, palladium or silver content of an item. It is therefore a legal requirement to hallmark all articles\" described as those metals. Under the Hallmarking Act 1973 a full UK hallmark has three compulsory parts: the sponsor's mark, the metal and fineness mark giving the millesimal number, and the mark of the assay office that tested and struck it.",
"Watch cases are treated separately in Switzerland. The Federal Office for Customs and Border Security states that \"All watch-cases in gold, silver, platinum or palladium, of foreign or local manufacture, sold in Switzerland, are subject to control and compulsory official marking\", and that \"A single official hallmark will be used for all precious metals and all fineness standards, the 'head of a St. Bernhard dog'\", struck with the symbol of the assay office concerned.",
"There is an international layer. The Convention on the Control and Marking of Articles of Precious Metals, known as the Hallmarking Convention, was \"signed in Vienna in November 1972 and entered into force in 1975\". Its device is the Common Control Mark, \"the first international hallmark and accepted in all the Convention's Contracting States\": an article carrying it and meeting the legal fineness may \"enter their territory without additional control or marking\".",
"India's scheme is the newest of the three. BIS records that since 1 July 2021 the hallmark on gold jewellery consists of the BIS logo, the purity in caratage and fineness, and a Hallmark Unique Identification number, \"a six-digit alphanumeric number which is unique for each hallmarked item and is traceable\"."
],
"related": [
"fineness",
"assay-office",
"watch-case",
"caseback"
],
"sources": [
{
"tier": 1,
"citation": "Bureau of Indian Standards, \"Hallmarking FAQs — General\"",
"url": "https://www.bis.gov.in/hallmarking-overview/hallmarking-faqs/hallmarking-faq/?lang=en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "UK Government (Department for Business and Trade), \"Hallmarking guidance notes\"",
"url": "https://assets.publishing.service.gov.uk/media/63a333b9d3bf7f37654767e0/hallmarking-guidance-notes.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Federal Office for Customs and Border Security (BAZG), Precious Metals Control, \"Official controlling and hallmarking\" (watch cases)",
"url": "https://www.bazg.admin.ch/en/precious-metal-control-watch-cases",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Hallmarking Convention, \"Control and Marking of Articles of Precious Metals — What is the Convention\"",
"url": "https://hallmarkingconvention.org/en/about-what-is-the-convention",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Assay office",
"slug": "assay-office",
"aliases": [
"assay offices",
"precious metals control office",
"assaying and hallmarking centre"
],
"domain": "trade",
"status": "verified",
"short": "The official body that tests articles of precious metal for fineness and strikes the hallmark, and whose own mark records which office did the work.",
"full": [
"An assay office is the body that does the testing and the striking. The UK government's hallmarking guidance lists the assay office mark as one of the three compulsory components of a UK hallmark, identifying which of the four UK offices tested and marked the article; each office also keeps the register of sponsors' marks it has approved.",
"In the United Kingdom the offices are supervised rather than run by a central body. The British Hallmarking Council states: \"We supervise the hallmarking activities of the 4 UK Assay Offices to ensure there is adequate provision of hallmarking within the UK.\" Its duties include \"working with the assay offices and Trading Standards to ensure that hallmarking law is enforced\" and \"monitoring the work of the UK assay offices and their established sub-offices\". The four are the Birmingham Assay Office, the Edinburgh Assay Office, The Goldsmiths' Company Assay Office and the Sheffield Assay Office.",
"Switzerland, where watch cases must be marked, runs the function inside its customs administration. The Federal Office for Customs and Border Security lists the Central Office for Precious Metals Control at Brügg together with precious metals control offices at Biel, La Chaux-de-Fonds, Chiasso, Geneva and Zurich, and notes that not all of them carry out analyses or official hallmarking.",
"India uses a network of recognised centres rather than a few statutory offices. The Bureau of Indian Standards recognises Assaying and Hallmarking Centres, which apply to it for that recognition, and points to IS 15820:2009, \"General Requirements for Establishment and Operation of Assaying and Hallmarking Centres\", as the standard they work to."
],
"related": [
"hallmark",
"fineness",
"watch-case",
"swiss-made"
],
"sources": [
{
"tier": 1,
"citation": "British Hallmarking Council, \"About us\" (GOV.UK)",
"url": "https://www.gov.uk/government/organisations/british-hallmarking-council/about",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "UK Government (Department for Business and Trade), \"Hallmarking guidance notes\"",
"url": "https://assets.publishing.service.gov.uk/media/63a333b9d3bf7f37654767e0/hallmarking-guidance-notes.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Federal Office for Customs and Border Security (BAZG), \"Locations of precious metals control in Switzerland\"",
"url": "https://www.bazg.admin.ch/en/precious-metal-control-switzerland-addresses-and-contacts",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Bureau of Indian Standards, \"Hallmarking overview\"",
"url": "https://www.bis.gov.in/hallmarking-overview/?lang=en",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Fineness",
"slug": "fineness",
"aliases": [
"millesimal fineness",
"karat",
"carat"
],
"domain": "trade",
"status": "verified",
"short": "The proportion of precious metal in an alloy, written in parts per thousand: 750 for 18-karat gold.",
"full": [
"Fineness is a proportion, not a quality. The UK government's hallmarking guidance describes the second compulsory part of a UK hallmark as the metal and fineness mark, giving \"the millesimal number (parts per thousand) indicating purity\". The standards it recognises are, for gold, 375, 585, 750, 916.6, 990 and 999; for silver, 800, 925, 958 and 999; for platinum, 850, 900, 950 and 999; and for palladium, 500, 950 and 999.",
"Karat is the same proportion counted out of 24 instead of 1,000. India's Bureau of Indian Standards, working to IS 1417:2016, permits six grades for gold jewellery and publishes both figures together: 14K at 585 parts per thousand, 18K at 750, 20K at 833, 22K at 916, 23K at 958 and 24KS at 995. A case marked 750 and one marked 18K make the same statement.",
"There is an international standard: ISO 9202:2026, Jewellery and precious metals — Fineness of precious metal alloys, edition 4, published May 2026, which \"specifies a range of fineness of precious metal alloys recommended for use in the field of jewellery\". What this Codex does not do: quote its table of grades. Only ISO 9202's abstract is public, so only that has been read; the millesimal figures above come from the UK hallmarking guidance and the caratage pairings from the Bureau of Indian Standards.",
"One word does double duty. A gemstone's carat is a mass, not a proportion. NIST writes that \"The carat (c) is another common measurement unit used in jewelry sales to measure gemstones. The carat had its origin in the carob seed, which later standardized a 1/444 ounce and then 0.2 gram (or 200 mg).\" So 0.2 g of diamond and the 18 parts in 24 that the Bureau of Indian Standards records as 18K gold are different quantities that share a name."
],
"autolink": false,
"autolink_note": "The aliases \"karat\" and \"carat\" would link every mention of a gemstone's weight to an entry about metal purity.",
"related": [
"hallmark",
"assay-office",
"watch-case"
],
"sources": [
{
"tier": 1,
"citation": "UK Government (Department for Business and Trade), \"Hallmarking guidance notes\"",
"url": "https://assets.publishing.service.gov.uk/media/63a333b9d3bf7f37654767e0/hallmarking-guidance-notes.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Bureau of Indian Standards, \"Hallmarking FAQs — General\" (IS 1417:2016 grades)",
"url": "https://www.bis.gov.in/hallmarking-overview/hallmarking-faqs/hallmarking-faq/?lang=en",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 9202:2026, Jewellery and precious metals — Fineness of precious metal alloys, edition 4, published May 2026",
"url": "https://www.iso.org/standard/90827.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "National Institute of Standards and Technology (NIST), \"Precious Metals Conversion Information\"",
"url": "https://www.nist.gov/pml/owm/metric-si/unit-conversion/precious-metals-conversion-information",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Manufacture",
"slug": "manufacture",
"aliases": [
"manufacture d'horlogerie"
],
"domain": "trade",
"status": "no-authoritative-definition",
"short": "A trade word for a firm that makes its own movements. No law or standards body the Codex could find fixes what it requires.",
"full": [
"The word is used constantly, and almost always of oneself. Jaeger-LeCoultre describes itself on its own site as \"one of the only true Manufactures with the capacity to produce all its luxury watches in their entirety, from design to production\", \"Bringing together 82 workshops, 108 crafts and 235 techniques – including 69 signature ones - under the same roof\". That is the company's own claim about itself, cited here as evidence of how the word is used, not of what it means.",
"Swiss law does not appear to reach it. The Swiss Federal Institute of Intellectual Property records only two industry ordinances for Swiss indications of source, one for watches and one for cosmetics, and the watch ordinance regulates the words \"Swiss\" and \"Swiss made\". The Federation of the Swiss Watch Industry's own guide reproducing that ordinance contains no occurrence of \"manufacture\", \"manufacture d'horlogerie\", \"in-house\" or \"calibre maison\".",
"Nor does Swiss horological standardisation. The list of available NIHS standards published by FH contains nothing on the term. It does list two vocabulary standards (NIHS 02-03, Vocabulaire horloger – Partie 1: Définitions technico-scientifiques, and NIHS 02-04, Partie 2: Définitions technico-commerciales), and the second is where a commercial term might sit. The list gives titles only, so neither has been read here. That is the one door left open.",
"What this Codex does not claim: that the word is unregistered anywhere. Swissreg, the EUIPO register and WIPO's Global Brand Database were not successfully queried for this entry. And no instrument read here sets a threshold of any kind: no minimum proportion of components made in-house, no list of trades that must be practised on site, no auditor."
],
"related": [
"in-house-movement",
"swiss-made",
"mechanical-watch",
"quartz-movement"
],
"sources": [
{
"tier": 1,
"citation": "Jaeger-LeCoultre, \"History of Our Manufacture-Atelier\" (the company's own site, cited for its own usage only)",
"url": "https://www.jaeger-lecoultre.com/us-en/our-maison/manufacture-since-1833",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Federal Institute of Intellectual Property (IPI), \"Industry ordinances\" (Swiss indications of source)",
"url": "https://www.ige.ch/en/law-and-policy/national-ip-law/indications-of-source/swiss-indications-of-source/industry-ordinances",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Guide to the use of the designation 'Swiss' for watches\", version 5",
"url": "https://www.fhs.swiss/file/8/Guide_FH_v.5_en.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH / NIHS, \"Liste des normes disponibles\" (list of available Swiss horological standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "In-house movement",
"slug": "in-house-movement",
"aliases": [
"in-house calibre",
"calibre maison"
],
"domain": "trade",
"status": "no-authoritative-definition",
"short": "A trade term for a movement a brand presents as its own design and production. No authority the Codex could find defines the threshold.",
"full": [
"The search that fails for \"manufacture\" fails here too. The Federation of the Swiss Watch Industry's guide reproducing the Swiss watch ordinance contains no occurrence of \"in-house\" or \"calibre maison\"; the FH/NIHS list of available Swiss horological standards contains no standard on the term; and the Swiss Federal Institute of Intellectual Property records industry ordinances for watches and cosmetics only, the watch one governing the words \"Swiss\" and \"Swiss made\".",
"More useful is what the ordinance does say, because it is often read as though it settled the question. Its conditions are about place and cost. Article 1a requires that a watch's \"technical development has taken place in Switzerland\", that \"its movement is Swiss\", that \"its movement has been cased up in Switzerland\", and that \"final inspection by the manufacturer took place in Switzerland and at least 60% of the manufacturing costs is generated in Switzerland\". Article 2 requires the movement to have \"undergone technical development in Switzerland\" and to \"have been assembled in Switzerland\". None of these clauses names the firm that must do the work.",
"The consequence follows from the text. A watch can satisfy the ordinance, and carry \"Swiss made\", with a movement developed and built by a separate supplier; a movement designed and built entirely within one company outside Switzerland cannot carry it at all. The 60 per cent rule tests where cost arises, not who did the designing.",
"What is still unresolved: NIHS 02-04, Vocabulaire horloger – Partie 2: Définitions technico-commerciales, is the document whose stated scope, technico-commercial definitions, could cover a term of this kind. The FH list gives its title only, so it has not been read here."
],
"related": [
"manufacture",
"swiss-made",
"mechanical-watch",
"quartz-movement"
],
"sources": [
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Guide to the use of the designation 'Swiss' for watches\", version 5, reproducing the Ordinance of 23 December 1971",
"url": "https://www.fhs.swiss/file/8/Guide_FH_v.5_en.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "WIPO Lex, \"Ordinance of December 23, 1971, on the Use of the Designation 'Swiss' for Watches\", Switzerland, SR 232.119",
"url": "https://www.wipo.int/wipolex/en/legislation/details/19179",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH / NIHS, \"Liste des normes disponibles\" (list of available Swiss horological standards)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Swiss Federal Institute of Intellectual Property (IPI), \"Industry ordinances\" (Swiss indications of source)",
"url": "https://www.ige.ch/en/law-and-policy/national-ip-law/indications-of-source/swiss-indications-of-source/industry-ordinances",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Counterfeit",
"slug": "counterfeit",
"aliases": [
"counterfeiting",
"counterfeit trademark goods"
],
"domain": "trade",
"status": "verified",
"short": "In trade law, goods bearing without authorisation a trade mark identical to, or not distinguishable from, one validly registered for those goods.",
"full": [
"The working legal definition comes from the WTO TRIPS Agreement. In the text set out in the WTO's own Analytical Index, the footnote to Article 51 defines counterfeit trademark goods as goods bearing \"without authorization a trademark which is identical to the trademark validly registered\" in respect of such goods, or a mark not distinguishable from it in essential aspects, thereby infringing the owner's rights under the law of the country of importation. The WTO's overview of TRIPS enforcement is shorter still: counterfeit trademark goods are \"Goods involving slavish copying of trademarks\", as against pirated copyright goods, \"Goods which violate a reproduction right under copyright or a related right\".",
"The definition matters because it triggers border machinery. Article 51 requires Members to \"adopt procedures to enable a right holder ... to lodge an application in writing ... for the suspension by the customs authorities of the release into free circulation\" of such goods, and customs must be able to detain them and to order \"destruction or disposal outside the channels of commerce of infringing goods\". The World Customs Organization states that \"The role of Customs in combating counterfeiting is very important to prevent unfair competition and guarantee equal market access to all business actors.\"",
"For watches, the Federation of the Swiss Watch Industry FH publishes the industry's own figures and legal position. FH states that \"Tens of millions of fake Swiss watches are offered for sale every year, while the Swiss watch industry produces around 30 million original watches\" (both figures are FH's own) and records that \"In Switzerland, as in many other countries, importing a counterfeit watch is forbidden by law, even in the case of one-off pieces bought in good faith for private use.\"",
"What this entry does not do: describe how counterfeits are made or how they may be told apart from genuine watches. It records the legal definition and the enforcement framework, and stops there."
],
"related": [
"swiss-made",
"geographical-indication",
"hallmark"
],
"sources": [
{
"tier": 1,
"citation": "World Trade Organization, WTO Analytical Index, TRIPS Agreement, Article 51 (including footnote defining counterfeit trademark goods)",
"url": "https://www.wto.org/english/res_e/publications_e/ai17_e/trips_art51_jur.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "World Trade Organization, \"Overview: the TRIPS Agreement — Enforcement\"",
"url": "https://www.wto.org/english/tratop_e/trips_e/intel2b_e.htm",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "World Customs Organization, \"Intellectual Property Rights\" (Enforcement and Compliance)",
"url": "https://www.wcoomd.org/en/topics/enforcement-and-compliance/activities-and-programmes/ipr.aspx",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH, \"Stop the fakes!\"",
"url": "https://www.fhs.swiss/eng/stopthefakes.html",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Crystal",
"slug": "crystal",
"aliases": [
"watch glass",
"sapphire crystal",
"mineral glass"
],
"domain": "materials",
"status": "verified-with-open-question",
"short": "The transparent cover over a watch dial, made of synthetic sapphire, mineral glass or acrylic.",
"full": [
"Two standards series cover the part, and both name only two of its three materials. ISO 14368-3:2003, Mineral and sapphire watch-glasses — Part 3: Qualitative criteria and test methods, edition 1, published August 2003, \"specifies the nomenclature of defects and the test methods to check them, with minimum physical and aesthetic requirements, for circular mineral and sapphire watch-glasses\". The Swiss horological standards list published by FH carries a parallel four-part series, NIHS 61-11 to 61-14, Verres de montres minéraux et en saphir, covering dimensions and tolerances, fixing to the case by adhesive or gasket, qualitative criteria, and anti-reflective treatment. Acrylic appears in neither series.",
"Sapphire in a watch is synthetic corundum: aluminium oxide, written Al2O3. The Handbook of Mineralogy (a mineralogical compilation issued by Mineral Data Publishing, not a standards body) gives corundum's formula as \"Al2O3\", its hardness as \"Hardness = 9\" on the Mohs scale, and its measured density as \"D(meas.) = 3.98–4.10\". Nine is the value for the mineral species, on a comparative scratch-resistance scale; it is not a measure of toughness or of resistance to a blow.",
"What this Codex does not do: give Mohs figures for mineral glass or for acrylic. No mineralogical or standards authority publishing values for those two materials was located and read, so the numbers that circulate in the trade are not repeated here. Only the titles and published scopes of the ISO and NIHS texts have been read; their full texts have not.",
"A note on the word. \"Crystal\" here is a trade name for the cover over the dial, and has nothing to do with the quartz crystal whose vibration sets the frequency of a quartz movement."
],
"autolink": false,
"autolink_note": "Autolinking \"crystal\" would wrongly link the words \"quartz crystal\", which means something else entirely.",
"related": [
"watch-case",
"dial",
"bezel",
"gasket"
],
"sources": [
{
"tier": 1,
"citation": "ISO 14368-3:2003, Mineral and sapphire watch-glasses — Part 3: Qualitative criteria and test methods, edition 1, published August 2003",
"url": "https://www.iso.org/standard/31462.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH / NIHS, \"Liste des normes disponibles\" (NIHS 61-11 to 61-14, mineral and sapphire watch glasses)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Handbook of Mineralogy, \"Corundum\", Mineral Data Publishing, version 1 (2001–2005), a mineralogical compilation, not an issuing standards body",
"url": "https://www.handbookofmineralogy.org/pdfs/corundum.pdf",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "medium"
},
{
"term": "Luminous material",
"slug": "luminous-material",
"aliases": [
"Super-LumiNova",
"photoluminescent pigment",
"lume"
],
"domain": "materials",
"status": "verified",
"short": "The pigment applied to hands and dials so they can be read in the dark; the modern kind is a strontium aluminate that is charged by light.",
"full": [
"The modern material is a ceramic pigment that stores light and gives it back. RC Tritec of Teufen, Switzerland, states in its own history that in the early 1990s Albert Reinhard Zeller \"developed a ceramic afterglow pigment based on strontium aluminate doped with rare earth elements\", and that this became Swiss Super-LumiNova®. The same history sets that against what the firm used before: Radium Chemie AG was founded in 1934 and made radium-based luminous paint thereafter, the page giving no start year for it, and then turned to tritium, since \"In 1961, Radium Chemie AG was the first manufacturer to be granted an import licence for the American watch market with the new phosphor technology activated by tritium.\" Super-LumiNova is a named company's trademarked product, and these are that company's statements about it.",
"Swiss horological standardisation covers the coating. The list of available NIHS standards published by FH includes NIHS 97-21, Instruments de mesure du temps – Dépôts photoluminescents – Méthodes d'essais et exigences, test methods and requirements for photoluminescent deposits on timekeeping instruments. The list gives its title only, so none of its requirements is quoted here.",
"The nearest thing to an international requirement is indirect. ISO 6425:2018, Horology — Divers' watches, edition 4, published October 2018, applies to watches that include \"a secured measuring system to indicate the diving time, which is visible in darkness\". That makes readability in the dark a condition of the divers' watch standard without naming the material that achieves it. Only the standard's published scope has been read; the text is paywalled.",
"Radioactive luminous materials are a separate, licensed category. Under United States regulation, 10 CFR 30.15 exempts from licensing timepieces containing not more than \"25 millicuries of tritium per timepiece\", \"5 millicuries of tritium per hand\" and \"15 millicuries of tritium per dial (bezels when used shall be considered as part of the dial)\", with much lower limits for promethium-147. A pigment charged by light is subject to no such limit."
],
"related": [
"radium-dial",
"divers-watch",
"dial",
"crystal"
],
"sources": [
{
"tier": 1,
"citation": "RC Tritec AG, \"History – RC Tritec Teufen\" (the manufacturer's own site, cited for its own products)",
"url": "https://www.rctritec.com/en/history-1",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Federation of the Swiss Watch Industry FH / NIHS, \"Liste des normes disponibles\" (NIHS 97-21, photoluminescent deposits)",
"url": "https://www.fhs.swiss/file/33/normes_disponibles.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "ISO 6425:2018, Horology — Divers' watches, edition 4, published October 2018",
"url": "https://www.iso.org/standard/66517.html",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "US Nuclear Regulatory Commission, 10 CFR 30.15, \"Certain items containing byproduct material\", Code of Federal Regulations",
"url": "https://www.ecfr.gov/current/title-10/chapter-I/part-30/subject-group-ECFR3d5ab53c21ba51d/section-30.15",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
},
{
"term": "Radium dial",
"slug": "radium-dial",
"aliases": [
"radium paint",
"radioluminescent dial"
],
"domain": "materials",
"status": "verified",
"short": "A dial or set of hands painted with radium-based self-luminous paint, used until about 1970; such items remain radioactive.",
"full": [
"Radium paint glowed without being charged, because it was radioactive. The US Nuclear Regulatory Commission states that \"Ra-226 was used until the late 1960s/early 1970s in self-luminous paints for watches, aircraft switches, clocks, and instrument dials\", and that \"The half-life of Ra-226 is 1600 years.\" The US Environmental Protection Agency states that \"Antiques containing radioactive material may continue to emit very low-levels of radiation for thousands of years, if not longer.\"",
"The painting was done by hand, and that work is why radium paint is remembered. The Science Museum Group (a museum publication, not a regulator) records that from 1917 women were employed to paint dials for the United States Radium Corporation in New Jersey, the Radium Dial Company in Illinois and the Waterbury Clock Company in Connecticut, and that they \"were encouraged to use the lip-pointing technique, pressing the brush between their lips to form a fine point before they dipped it in the paint. Every time this was done, a small amount of radium was ingested.\" The consequences it records: \"Their teeth would ache and eventually fall out... They began to develop severe anaemia. Their bones went brittle. Eventually, jaw necrosis set in.\"",
"The litigation changed the law more than it compensated the claimants. Each of the women in the settled case \"was awarded $10,000 in damages and $600 per year for the rest of their lives\", while \"United States Radium would not have to take any legal responsibility\". Afterwards, \"Lip pointing was banned, and protective equipment was introduced for all workers\", and \"Legislation was introduced to crack down on commercial radium products and to recognise radium poisoning as a compensable occupational disease.\"",
"Such watches still exist and are still regulated. The NRC states that \"Any individual intact timepiece containing less than 0.037 megabecquerel... of radioactivity is exempt from regulatory requirements.\" The Museum of Radiation and Radioactivity, describing a 1927 radium-dial watch in its collection, notes that \"Estimates of the average dose to the gonads for someone wearing such a watch ranged from 0.5 to 3 mrem per year.\" This Codex gives no instruction about what to do with such a watch; it records only what the regulator and the museum state."
],
"related": [
"luminous-material",
"dial",
"crystal"
],
"sources": [
{
"tier": 1,
"citation": "US Nuclear Regulatory Commission, \"Frequently Asked Questions (FAQs) Regarding Radium-226\"",
"url": "https://www.nrc.gov/sites/default/files/documents/radium_faq102008.pdf",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "US Environmental Protection Agency, RadTown, \"Radioactivity in Antiques\"",
"url": "https://www.epa.gov/radtown/radioactivity-antiques",
"accessed": "2026-09-26"
},
{
"tier": 1,
"citation": "Museum of Radiation and Radioactivity (Oak Ridge Associated Universities), collection record, \"Radium Dial Watch\"",
"url": "https://www.orau.org/health-physics-museum/collection/radioluminescent/watch.html",
"accessed": "2026-09-26"
},
{
"tier": 2,
"citation": "Science Museum Group, \"The Radium Girls\", a museum's own publication, not the issuing regulator",
"url": "https://blog.sciencemuseumgroup.org.uk/the-radium-girls/",
"accessed": "2026-09-26"
}
],
"last_verified": "2026-09-26",
"review_due": "2027-03-26",
"confidence": "high"
}
]
}