The no-decompression scale — called no-deco scale in English texts — is not a decorative element: it is a survival tool engraved on the bezel. It indicates the maximum time a diver can remain at a given depth without being obliged to perform decompression stops during ascent. The values derive from US Navy tables, developed starting in the 1950s, which establish the limits of dissolved nitrogen in the blood compatible with a direct ascent to the surface.
Doxa was the first manufacturer of civilian watches to adopt this graduation on the Sub 300 bezel, presented in 1967. The layout is dual-ring: the outer ring shows depths (in feet for versions intended for the North American market, in meters for European ones), while the inner ring shows the maximum minutes allowed at that depth. Reading is immediate: no calculations needed, you simply need to keep your wrist underwater. Doxa patented this system applied to the watch bezel, and the project was born from direct collaboration with professional divers, not from a marketing intuition. Brands like Jenny and Ollech & Wajs moved in the same direction in subsequent years, with their own geometries but with the same functional logic.
Be careful of a frequent confusion in catalog notes and forums: no-deco is read as an abbreviation of no decoration, meaning a bezel without ornamental elements. The misunderstanding is not entirely unfounded — a functional scale, by definition, eliminates everything that is not necessary — but the origin of the term is exclusively technical. A plain blue bezel without graduation is not a no-deco scale: it is simply a solid bezel.
Another point worth clarifying: not all Doxa watches feature the no-decompression scale. The Army model, for example, uses the classic 60-minute sexagesimal scale, suitable for measuring elapsed time in any context, not just diving. The presence or absence of the no-deco scale substantially changes the watch's intended use profile and, in the vintage market, affects the piece's value. I have seen original Sub 300 examples pass through dealers with the bezel replaced with a sexagesimal one: the watch loses its technical identity before losing its collectible identity.
I am not aware of any other manufacturers having filed equivalent patents before Doxa on this specific application to the rotating bezel. On standalone instruments — laminated tables, dive slates — the no-deco logic already existed. But transferring it to the watch bezel was a choice made by Doxa, and this remains its documented historical paternity.