I have acquired this single shot break open rifle. On the top of the octagon barrel is stamped E C Green - Cheltenham - Gloster. There are no other markings visible. It is a centerfire with a straight wall chamber. It looks like about 30 caliber and a 32 Long Colt chambers nicely in it. The 32 S&W case is too large a diameter. Does anyone have any idea what cartridge this may have been made for?