I just got around to rebuilding the Mark II bolt today, and will finish reassembling the rest of the pistol some other time. Here's my old firing pin retaining pin. You can see that it's bent, but it looked worse to me IRL when I first took it apart. It also has a bad burr on it about a quarter of the way in from one end. I don't know if a round blew up and forced the firing pin back into it, or what happened. I don't remember any blow-ups, but may have shot a Ramset power load in the gun. Other than this pin being bent, and most of the extractor being gone, the bolt looked pretty good. But I replaced every part except the bolt body. The new recoil spring seems stronger than the old one, which may have been an original part. Besides being more well made, the firing pin seems to be thicker than stock but that didn't make it stick or anything like that.