In its span, it encompassed metal and plastic cased watches with both mechanical and quartz movements.
These were lower quality watches than the 15 jewel movements, the transition started as US involvement in Vietnam ramped up.
Regarding Revision B from 1976, it "added radiation symbols to the dial, indicating that the luminous markers were radioactive, H3 for tritium.
Revision D (1986) expanded the scope of the specification to encompass a wider range of watches.
In 1957 the DOD released MIL-C-18012A, a specification detailing the legibility of numerical displays for aircraft dials and readouts, and updated it with MIL-C-18012B in 1964.