Not that unusual to find 12 bore chambered guns with tight barrels measuring at 14 bore or even down to 15 from that early era. Just has black powder marks but not complete. The thing that puzzles me are the many stampings of the word 'England'. That sets the suspicious mind going. The butt plate design is about as non-English as you can get. May be spurious. As a gift it makes a nice wall piece. Lagopus.....