There is potential this is a cartridge conversion, I see no provision for percussion caps. The "missing piece" at the front of the frame held the loading lever retainer. The cylinder has been shortened, on the right side a loading gate appears to be attached to the recoil shield spacer. If so, a firing pin has been added to the hammer.
For movie buffs, as the character Will Muney, Clint Eastwood packed one around in "The Unforgiven".