Question re proof rules:
The "not for ball" on this gun tells us that it was proofed prior to the rules of 1887, which is when the fractional bore sizes (12/1, etc) came into use. Thus, prior to 1887, a gun could have a bore diameter of up to .750 (11ga starting at .751) and still be a 12. If that gun had been submitted for reproof when the fractional bore sizes were still in use, then the left barrel would have been marked 12/1. However . . . since 12/1 did not exist when the gun was originally proofed, would it now be judged to be out of proof because it is more than .010 over the .729 12ga standard?