I remember nickel and quarter slots in the EM clubs at Clark AFB, Phillipines and my Saigon hotel barracks in 1968, and also at the Korat US Army base in Thailand in 1965. My belief is they were quite common at larger overseas bases, at least in Asia. As I recall they were mostly Mills Hi-Tops and had such poor paybacks and low jackpots that they were not in use most of the time. No life-changing jackpots really did make it a form of entertainment and few bothered to try to get rich. Just $10 of fun every now and then as a diversion.