One note on the 13. It has been stated that the 13 indicates an original dia of .710. this is not entirely correct. In that era bores were simply checked with a series of plug gages & marked according to the largest one which would enter to a depth of 9" from the breech.
A 13 gauge plug diameter is .710" while next step up of 13/1 was .719". When this gun was proofed it accepted the 13 plug but not the 13/1. Actual diameter could have been anywhere in betwen.
The .719 mark at the re-proof does as I understand it mean an actual diameter of .719" by measurement. It may not have taken much honing at all to go from the 13 to the .719" bore.This may well have been done in preping for the re-proof.
