Ian
I didn't notice the HB over 1 inside a circle. I assumed (incorrectly) that the stamps on both sides of the lug were the same. Is it possible to determine the original proofing of the barrel? What does the 12 over a C inside a diamond, the 13, and the .719" refer to?
Thanks
Alan
OBTW, you said there doesn't seem to be a reproof mark and yet you indicated that the HB over 1 inside a circle says it was. Confused.

I found this from the Birmingham Proof House website:


I assume my gun was proofed sometime between 1925 and 1954 as the marks corresponds with the ones used from 1925 up to 1954?