A sterile dial means exactly what it sounds like: no government text, no unit insignia, nothing but a clean, readable face. Reference WW194004BK-0802 is the Marathon GPQ in black with that sterile layout, a 34mm Swiss quartz tritium watch made for clear reading after dark.

The tritium is the star. Marathon fits self-illuminating gas tubes to the hour markers and hands, and they glow continuously without exposure to light, rated for up to roughly 20 years. Unlike painted lume, there is no fade toward morning; at 4 a.m. the dial is as legible as it was at midnight. On a sterile dial, those glowing tubes are framed by nothing more than numerals and 12- and 24-hour scales, which gives the GPQ its uncluttered look.

Timekeeping comes from the Swiss ETA F06.115 HeavyDrive quartz, a high-torque movement with an end-of-life battery indicator. The black fibreshell composite case measures 34mm and 11.5mm thick and is made to MIL-PRF-46374G, Type I, Class 1, with sapphire crystal and a pressure crown. This listing comes on an 11-inch black one-piece nylon strap, giving a little more length for larger wrists or wearing over a sleeve.

WW194004BK-0802 Key Specs

• Model: Marathon General Purpose Quartz (GPQ), black, sterile
• Case: black composite fibreshell, 34mm, 11.5mm
• Movement: ETA F06.115 HeavyDrive high-torque Swiss quartz, EOL indicator
• Water resistance: 3 ATM
• Crystal: sapphire
• Illumination: tritium gas tubes, rated up to ~20 years
• Strap: black one-piece nylon, 11", 16mm lug width

Clean by day, glowing by night.