I've been going over pictures of coins in my collection, and I noticed what appears to be doubling in States on the reverse of this Kennedy half. I promise to do my best and get pictures of the obverse when I get home in a few months. I'm going through pictures on my computer to see if I can find a picture of the obverse. So far no luck. Is it doubling, or is the lighting just making it look that way?
I can't tell from your photo, but if I were to hazard a guess, I would say it is machine doubling. Machine doubling is very common on Kennedy halves of the 70's. Chris