Texasbdog,
Take a look at my comments back on page 2. If the 16 gauge shells that came with it are 2 1/2 or 2 1/16" , that would be correct. If they are 2 3/4", you should check to see if the chamber has been lengthened without being marked. The 9.3x72R cartridges would be one of the cartridges consistent with the markings. If they chamber, that would rule out any of the shorter cartridges. While not very likely, it could be chambered for either 9.3x75R( the 360 base one) or 9.3x82R Nimrod. A chamber cast would be necessary to rule these out. Firing 9.3x72 R ammo in either of these wouldn't likely be dangerous, but it might not be very accurate in a 9.3x82R chamber.
Mike