Omega Speedmaster Professional

The "Moonwatch" is aptly named for the fact that is was the watch worn during the first American spacewalk during Gemini 4. It was also the first watch worn on the moon during Apollo 11. The Speedmaster Professional is one of several watches still qualified by NASA for spaceflight, but is still the only one qualified for EVA (extra-vehicular activity or work done outside the spacecraft and away from Earth).

Before Gemini 3, bids of several brands were officially solicited to NASA, including Breitling, Rolex, and Omega, as well as others that produced mechanical chronographs. The contenders that were accepted by NASA were Rolex, Longines-Wittnauer, and Omega. For use in space these watches had to pass the following tests:

High temperature: 48 hours at 71° C followed by 30 minutes at 93° C
Low temperature: Four hours at -18° C
Temperature cycling in near-vacuum: Fifteen cycles of heating to 71° C for 45 minutes, followed by cooling to -18° C for 45 minutes at 10-6 atm
Humidity: 250 hours at temperatures between 20° C and 71° C at relative humidity of 95%
Oxygen environment: 100% oxygen at 0.35 atm and 71° C for 48 hours
Shock: Six 11ms 40 G shocks from different directions
Linear acceleration: from 1 to 7.25G within 333 seconds
Low pressure: 90 minutes at 10-6 atm at 71° C followed by 30 minutes at 93° C
High pressure: 1.6 atm for one hour
Vibration: three cycles of 30 minutes vibration varying from 5 to 2000hz with minimum 8.8G impulse
Acoustic noise: 30 minutes at 130db from 40 to 10,000hz

The Speedmaster was the watch selected on March 1965 because it passed the tests while remaining within 5 seconds per day rate (it lost no more than 5 seconds a day).