Caseback

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.