Revolver gun. Small bronze cylinder at bottom is a cover for drive pinion, handle allows it to be opened like a cylinder-top desk for cleaning, lubrication. Driven by square crank fitting at rear. Pinion engages ring gear which encircles the cylinder containing at least three chambers, like revolver cylinder. Percussion nipples are on rear of cylinder, cylinder is inside the visible bronze housing/dust+rain cover. Complete housing containing cylinder was removeable for reloading, by handle attached to the projection with hole which you can see in the photo. Extra cylinders would be available and kept loaded. The slot in the rear of the breech had spring-loaded pawl which engaged aligment slot in rear of cylinder when chamber aligned with bore, press to disengage in order to rotate crank and bring next chamber into aligment with bore for firing. Hammer at rear fires caps. Hammer and pawl/pawl spring are missing.