The average Vietnam Vet (let's say 20 years old in 1970) would have been 40 when I was 14. One of my friends Dad was pretty messed-up. I laugh hard when I see guys my age, or just a bit older, rocking the "Vietnam Veteran" hat and "woe is me" act- such a scam.

I got busted by a Navy O1 wearing the white short sleeve dress shirt with the shoulderboards- "Aren't you supposed to salute an Officer?" At that time, 99.9% of my exposure had been to Army personnel, so my response was genuine- "Sorry Sir, I didn't recognize your rank".

In the OP's story, I would say it's probably 90% likely the bum was a scammer and 10% he was NAVY/AF.