Welcome to the BBS Azure. In order to consider firing it we need to see the proof marks and other information on the barrel flats. You have to take the barrels off to see that and get a picture.
When you lift the "ears" and pull back the action, you should see a flat spring on the action top. Depress that and push the barrels back to break the friction fit and remove the barrels. Then look on the flats underneath the breech and tell us or better make a picture of what's stamped there.
There's lots of knowledgeable folks here who can tell maybe who built your gun, what the chamber length is, and what powder it was proofed for. From that you can tell what shells to try...Geo
Careful, I'd bet it isn't chambered for 2 3/4" shells!
