I've just inherited an interesting dbl barrel. Markings indicate: "John A.D. Heckenbach's Breech Loader, Patented June 22, 1869, Mayville, Dodge Co, Wis." The breech mechanism is rather complicated in that it extends about an inch before the barrels pivot downwards. I can't really imagine what the cartridge looked like, but I suspect it came from a different planet, devoid of DNA-based life forms.

I will post a few photos as soon as I can figure out how to make that happen . . .