US Government Specification Field Watch

First published on 30 October 1964 and revised through 1989. Two orthogonal axes govern what a given watch should be, and both are needed: the REVISION LETTER (A to E) sets the era, the permitted manufacturers and the dial and caseback markings, while the TYPE number sets the movement. Types 1 and 2 are mechanical; Types 3, 4 and 5 are quartz. Type 1 requires a minimum of 15 jewels and ±30 seconds a day at 75°F; Type 2 sets no specific movement requirement and allows ±60 seconds a day, and is the characteristically plastic, disposable execution.