The one pictured in this review was issued by USAF in 1988. The watch was actually produced under government contract by Marathon Watch Co. based in Ontario, Canada, measures 47.8MM lug to lug and 43.8MM across the crown diameter. It houses a Swiss made quartz movement.
The styling of the watch is very similar, if not identical, to USAF issue Marathon Military Pilot's Watch. Adanac is the predecessor to that model, albeit without the tritium vials. A careful reader might have noticed that "Adanac" is Canada spelled backwards.