38 caliber, 6 shot Spanish pinfire pistol with retractable knife blade manufactured circa 1860-1869.
Marked 56 near folding trigger on the left side.
Approximate overall length: 9 inches with blade retracted, 12 inches with blade extended. The barrel is approximately 4 inches long, and the blade is approximately 3 inches long.
Pinfires were a short-lived European designed cartridge. As the name implies, a small pin sticks out of the side perpendicular to the cartridge. Note the small rectangular holes at the barrel breech where the pin in the cartridge sticks out. The hammer hits the top of the pin, pushing it into the cartridge and igniting the powder.