If your gun was built per-1896 it likely has only black powder proofs which show neither chamber length nor weight of shot. If the gun is around 6 1/2 lbs it was built as a game gun and almost certainly had 2 1/2" chambers.It is because the early proof marks did not give the full story that they were upgraded over the years.BTW the 12 over LC (long chamber)in the gauge diamond refers to 3" or longer. My Scott pigeon gun has one set of original 1 1/4 oz. nitro proof marks, measures 2 3/4" and is stamped 12 over C.in the diamond.

Better to keep your mouth shut and be thought stupid,than open it and confirm.