Welcome Alan. You have a No. 00 with Armor Steel (fluid steel) barrels (which became the Field grade in 1913), and yes the chambers were originally 2 3/4". The chambers should be measured to be sure they have not been modified however.

Please review the FAQs, esp. "Is my gun safe to shoot", and the Shotshells and Shooting section
https://lcsca.clubexpress.com/content.aspx?page_id=274&club_id=43784

ANY 110 year old gun needs to be evaluated by a double gun specialist before use, with attention to the stock for cracks. If you intend to use the guns with heavy waterfowl or buckshot loads, it would be wise to have the head of the stock glasbedded.