John,
The 67/49 is the bore(not groove or bullet)diameter, expressed in gauge measurement( about 10.41mm). A gun marked this way would have been made between 1893 and 1912. It is chambered for 16 ga 65mm (2 1/2-2 9/16")shells, and both barrels are choked but the constriction is not known. Did the dimensions come from a chambercast or direct measurement? If there is no chambercast, you should make one. The dimensions you gave could fit a nominal 10.75x50R, but there would be several cartridges that fit that general description and a chamber cast may help ID it. There is a mark just above the 67/49, that does not seem to be a proof mark. I don't recognize it, maybe Raimey does.
Mike
