Cavediver, the barrel flats will tell you on that late a pair if they were proofed and chambered for 2 3/4 shells. Would not be surprised if they were and suspect they are proofed for 1 1/8 ounces of shot. ....
Actually 1 1/8 ounce proofs were for 2 1/2" chambers. 1 1/4 ounce proofs were 2 3/4" chmabers. Actual chamber length would not have been marked with proofs of that timeframe. The 2 3/4" chamber stamps had to be a later reproof or newer/sleeved barrels after approx. 1925.
The other piece of advice to cavediver that has been missing so far is the STRONG advisement to have the guns checked out by a qualified Double oriented gunsmith before shooting anything with them.