Waterproof wristlet watch
The waterproof wristlet watch (WWW) standard for wristwatches by the Ministry of Defence (United Kingdom) is believed to be one of the first official standards for a military issue watch. Timekeeping in disciplines such as navigation, and warfare have always been of vital importance. Mechanisms for telling things such as direction, star position, and time on boats date back to antiquity, but World War I was the first time that soldiers wore timepieces on their wrists in the form of trench watches. The obvious characteristics of a trench watch were that they were repurposed small sized (size 0, 7.5 ligne, 29.62mm) pocket watches protected with crude metal used to protect the glass crystal covering the dial.
The invention of the trench watch precipitated the invention of the wrist watch, and these watches were adopted by both the public and the military.
With the invention of the wrist watch came the British military issuing a standard for military wrist watches. This is referred to as the WWW standard. These were characterized by small, simple movements. Among the requirements were matte black dials with luminous hands, numbers and indices, subsidiary seconds, shatter-resistant perspex plastic crystal, a case resistant to water, dust and shock, and a high-quality, isochronal and robust, 15 jewel movement, and a water resistant winding crown of a good size. Twelve companies (Buren, Cyma, Eterna, Grana, IWC, Jaeger LeCoultre, Lemania, Longines, Omega, Record, Timor, Vertex) responded with conforming designs for what are commonly called WWWs (watch(es), wristlet, waterproof) or Mark X (after the IWC version?). They also featured the typical British military "Broad Arrow" on both the dial, and the case back.