Once Again; 3" shells were in use long before 1923. They were "NOT" the heavy loaded SuperX Magnums which were introduced in the 1920's, don't recall for certain if 1923 is the exact date or not. The fact that it has 3" chambers now is not an absolute guarantee it has been re-chambered. Nash Buckingham wrote of using his Father's gun when he was growing up, which as I recall was from the 1880's & chambered for 3¼" shells. It was a Greener Hammer gun but they acquired American loaded shells for it, loaded with the "Heavy Load" of 1oz shot. Several American makers adopted the 2 3/4" shell as standard quite early on while others stayed with the 2 5/8". In 12ga lengths from 2½" through 3¼" were available on order in 1/8" increments As I stated in my earlier post the primary difference was in the amount of wadding used, not necessarily heavier loads.
I am in total agreement I would treat this ol gal kindly & not put heavy loads through her, either most modern 2 3/4" or 3" ones.
