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.

Other requirements included a matte black dial with luminescent hands, numbers and indices, subsidiary seconds, a shatter-resistant perspex plastic crystal, a case resistant to water, dust and shock, a high-quality, isochronal and robust, 15 jewel movement, and a water-resistant winding crown of a good size.

[1] 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), Mark X (after the IWC version), or colloquially 'the Dirty Dozen'.

All featured the typical British military broad arrow on both the dial and the case back.