Allen & Wheelock/Ethan Allen Single-Shot Center Hammer
Single-shot derringer-type pistol. Chambered for .22-caliber rimfire cartridge. Had part-octagon barrels from 2" to 5.5" in length that swung to right side for loading. Some had automatic ejectors, others did not. Frame brass or iron, with bird's-head or squared butt walnut grips. Marked, "Allen & Wheelock" or "E. Allen & Co.". Very few manufactured in early 1860s.
Full-length octagon barrel. Round iron frame. Rarely encountered.