printing proofs are usually cards which are created in the first print run as tests - sometimes they are only one color, so the cards i got, one was all blue and one was all green and one was blank, but the backs were all finished - they can sometimes be missing parts of images which do not need that color - there are cards out there which may be labeled as a proof, but really are not, some trading card manufacturers even "produce" them, but really, they arent proofs, just "chase" cards - quite often a proof will be a little... not right - maybe a crooked image, or misprinted word, mispellings etc...