Hallmark

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".