the Glycine Airman has always been one of my favourite 24hr watches along with its competitor, the O&W earlybird.
as i mentioned in the wristscan, i have owned one, let it go and now looking at a couple more that are nearly from 1964. i dont know if you found it, but there is an excellent reference on the web identifying the different changes in models andthe years they were made.
the model i am looking at has a 25 jewel A.Schild 1700/01 movement. other markers on it date it from 64-67, but it has unmarked flat crowns which were changed to cross hatched crowns in 1965. however, they could easily have been retro fitted during service so i cant say it is a 64. luckily i have a 24 hr watch theme as well so the date isnt a deal breaker.
neither of the two i am looking at are in the condition yours is in. close, but not quite as good so you have found a really good one.
i'm lucky enough to have its competitor also much loved by pilots during the Vietnam war, the Earlybird.
enjoy
Graham