It is likely that the barrels of your pre-1913 No. 2 were replaced with post-1913 Armor Steel Field grade barrels, possibly because the originals were damascus, or were damaged. In that the SNs match, the replacement was likely done by Hunter Arms, and the work may be documented with a Research Letter.
The cost of replacement barrels was about 1/2 of what the gun of that grade would be. This is from 1910 and Armor Steel was significantly less than Crown Steel