No-Deco Scale

The no-deco scale is not a decorative element: it is a underwater safety tool engraved or printed on the rotating bezel of a diving watch, indicating the maximum time you can spend at a given depth without requiring decompression stops during ascent. The name comes from the English term no-decompression limit—the threshold within which a diver can surface without following an intermediate stop protocol to expel nitrogen dissolved in the bloodstream.

The scale structure is almost always a dual ring: the outer ring displays depth (in feet for US Navy versions, in meters for European versions), while the inner ring shows the permitted bottom time at that depth. Reading is direct and requires no additional calculations: you look at your maximum depth, follow the corresponding line, and read your remaining time. In water, wearing gloves with reduced visibility, this simplicity is as valuable as water resistance itself.

Doxa was the first manufacturer to systematically integrate a no-deco scale on the bezel of a series-production watch, starting with the SUB 300 in 1967, developed in collaboration with professional divers and based on US Navy decompression tables. The shark-toothed bezel with patented no-deco scale became the technical standard for the industry. Other makers, including Jenny and Ollech & Wajs, adopted similar solutions in the following years. The Doxa Army model, by contrast, used the classic 60-minute scale without decompression data.

From my workbench, I've seen considerable confusion around this term. Some sources use "no-deco" to simply describe a bezel without graphic decoration, which is technically incorrect. Others apply it to any unidirectional bezel, confusing function with mechanics. The no-deco scale is a precise thing: a graduation derived from medical-military tables, not a stylistic choice. The Synchron Ti300M Poseidon, for example, features a unidirectional 120-click bezel with a true no-deco scale, faithful to the original specification.

An interesting and rare case: the 1985 Aqualand CQ-1012-50 printed the no-deco tables directly on the watch strap, as a field reference stamped into the material. A solution I have never seen replicated elsewhere.