Cannonmn,
This one fascinates me, I've never seen the like of it before. I know this is just pure speculation, but if I had to make a guess I'd say that this was scratch built by a good machinist/gunsmith who was satisfying his own imagination in designing it; at least I've never seen a similar breech mechanism made by Strong, Brown, Lavigne et al., not that I've seen a whole slew of these guns. Why is there such a dearth of sites with information on these salute cannons on the internet?