As seen on my journey

I was filling up the moving van the other day when a car pulled up behind me displaying a veteran license plate that read BTM TYM.

He saw me squinting at the plate (I was trying to make out the military branch insignia on it – US Navy) and we struck up a conversation.  He seemed like a friendly enough fellow and I found out he and I had gone through one training course that was the same (airborne training… yes, I used to jump out of perfectly good planes…), and I also found out he had a rather specific type of training.

While driving off after filling the fuel tank I had the thought that if this guy knew how a guy like me might read that plate, he wouldn’t have put it on his car.

So based on what I said above, what do you think the meaning is behind the message on his plate?  What was his occupation while in the military?