Don't forget that at the time this gun was proofed precise measurements of bore & choke were not made. A series of plugs were used to check the bore. The right bbl accepted a 13ga (.710") but not a 12ga (.729") so actual size could have been anywhere in between. The left bbl accepted a 12ga plug at breech but not an 11ga (.751")one & a 13ga plug at the muzzle, but not a 12ga. One thus cannot state precisely what ctual measurements were at time of proof, only that they fell within that range.

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