Note also that 12/1 kicks in at a bore of .740" diameter. Thus if it will accept a .740" plug gage to the required depth, 9" I believe, it would be "Out of Proof" for the original 12 marking. Assuming the .740" was stamped at the time of the later 3 - 1 1/8 black powder proof it would of course be In Proof for that load.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra