Nice two barrel set with the Watson. You can just see where someone at the Proof House accidently picked up the 1 1/4 oz. stamp and used that before realising the mistake and over stamping with 1 5/8 oz. Don't see many with that mark, the next common stamp would be for 1 1/2 oz.

eeb, sounds as if you have an old live pigeon gun. I have a hammer Jeffrey pigeon gun. Chances are that it will be well choked. Lagopus.....