Several guns have been discussed fairly recently which had 12 gauge chambers with barrels marked 14 (one was mine). These as I recall have all been guns made prior to the chamber marking, so the 14 is simply the largest size gage which would enter the bore at time of proof. 12 = .729", 13 = .710", 14 = .693" & 15= ..677".
This gun was also built prior to the "Tween" sizes as 14/1 etc. Thus at proof the bores were somewhere between .693" & .710" while the choke was between .677" & .693". It may very well have been built with a 12ga chamber.
Before Shooting it, though I would check the wall over the end of the chamber & be certain it is adequate.
