I have found a few proofs while searching for Halves. Most of them are in okay shape but they don't look like proofs I am used to seeing in the sets. Should I be keeping them? I am thinking to myself "I should save this, it's a proof!" but is there any market for Circulated Proofs? I found one that was pretty beat up so I put it back into circulation, I'd gladly however take a beat up 1970-D.
I like to put them back into circulation, maybe it will get somebody into collecting. Since you are already into collecting, and the proofs aren't of much value, maybe it is better for you to pass the bug onto somebody else.
Maybe I'll give them away. I'll probably hang on to them for a few years and when my son gets into Boy Scouts I'll give a few away at troop meetings as prizes.
I keep all the proofs I find even if they're beat up. Worst case scenario they're worth 0.50. If you sell on eBay, they're always a nice 'gift' to ship along with the original item as a thank you.