A beautiful, if plain, example in any case. If you ever decide to part with it, Nando, ole pal...
I'm sorry, I can't tell from the pic, is the swivel you mention small, as if for a sling strap, or larger, as if for a true mounting for a swivel. These types were also popular as 'wall guns' for forts, operating in much the same way as swivel guns on ships as you well know. I love the lock.