The Walch revolver was a Civil War era design with the unique feature of having superimposed loads - each chamber in the cylinder held not one shot, but two, stacked one on top of the other. The revolver had two hammers and a progressive trigger, and 10 percussions caps (for the 5-chamber model). This led to a 10-shot revolver in the size of a typical 5-shot one. Of course, since the chambers were split between two powder charges, the muzzle velocity was relatively low in comparison to other revolvers of the period.
This Walch 10-shot .31 caliber example has been modified by someone into a pepperbox style of pistol, with the barrel completely removed. This makes it substantially more compact, but also amplifies the problem of low muzzle velocity, and without any rifled bore at all, I’m sure accuracy suffers as well. Not that this was intended for use at any significant distance, of course...
Cool Forgotten Weapons merch! http://shop.bbtv.com/collections/forgotten-weapons