I really don't think anyone knows what is and isn't a PB boot even when seeing the boards of the game. I've yet to ever see one as all solid PROMS. If anyone has one out there, snap a picture, because I won't believe you if you don't show me some proof they really exist
A lot of people claim to have owned one or seen one, but can never show any proof of it. Second, SNK had to act fast to satisfy the demand for this game. That being the case, many believe here that "original" SNK PB carts may be hack jobs of just resoldering EPROMs onto a game's boards that didn't sell well. Whatever the case, it is easily the most difficult one to find as a "non-boot" at least in the way we think of them. As long as it is a clean game with no crazy wires running to and fro you should be fine.