I finally found the reference I was thinking of regarding the "11" marked on the proofs. It's from Greener's Modern Breechloaders:Sporting and Military from 1871, pages 40 and 41. He's talking about shotgun barrels here, but I think the same applied to rifles:

"All first-class shooting gunbarrels will be found marked 13-bore. This mark is at the breech-end, stamped at the proof-house. In all cases where barrels are not bored up to the size before being proved,the proof-house people mark them the size under. For instance, supposing the barrels to be 13-guage, they mark them No. 13; and again, if the No. 12 plug will not pass easily down the barrels the whole length, they still mark them No. 13. These marks are looked upon by some as denoting the exact bore of the gun, but this cannot always be depended upon.

All breech-loading barrels are fine-bored after they have received the proof-mark, in order to remove the indentations caused by stamping them at proof. It often happens that they are marked 13, and gauge full 12.

Some American sportsmen will insist upon having their guns marked 12 at the proof This is a great mistake. It is impossible for us to make a really first-class shooting gun so marked. The same remarks apply to guns of 10-bore. These should be marked 11-bore, which allows the barrels
to be, when finished, just under 10-bore."

John, on a curious note I discovered that my barrels have about .003" of choke in the last few inches. I made chamber casts when I got mine and tapped a ball from breech to muzzle through each barrel. It took a steady rapping with a mallet to do so. On a whim I decided to drive a pair in the other direction and was surprised when they fell freely to the chambered after 3-4 inches.

Bob