Thanks for the detailed info. I've pictured some of the proofs for interest. There is a small J.N. stamp in front of the wedge cage. I wonder if anyone knows anything about this stamp.

I did as suggested and super-glued the crack. I also used an old tapered plum bob with various grit papers (120 to 600) to bevel the muzzle. I did find that the wedge was years ago broken with half missing. (see pics) Not sure if this is a shooting issue or not.

http://www.buckstix.com/buckpics/8bore-proofs.jpg