Allen Type Percussion Single Shot Pistol

Percussion Single Shot Pistol remains in fine as found condition. Not sure who manufactured this pistol as I can not find a reference to it. Possible Allen, Blunt & Syms, Marston? . Overall length 11″ with a 6″ barrel with a knurled ring at the octagon to round section and at the flared muzzle. Actions are fine and bore has heavy rifling. C.1840