Wikipedia: The model 1805 U.S. Marshal "Harper's Ferry" flintlock pistol, manufactured at the Harpers Ferry Armory in Virginia (now West Virginia), was the first pistol manufactured by an American national armory. It was the standard handgun of the US dragoons during the War of 1812.
The Model 1805 horse pistol was copied from the French Pistolet Modele An. IX of 1798. Harper's Ferry models 1805, 1806, 1807 and 1808 flintlock pistols were all identical and there were no changes in design during this model year sequence. The M1805 pistol was a .54 caliber, single-shot, smoothbore, flintlock pistol intended for field duty. Pistols made for officers resembled the standard horse pistol but featured more elaborate decoration, and sometimes a rifled barrel. Harper's Ferry model 1805-1808 flintlock pistols were known then as “horsemen’s pistols” and were produced in pairs; both pistols having identical serial numbers. With just one shot readily available without reloading, a pair or "brace" was the standard issue. Horse accouterments also included a standard pair of saddle holsters. No serial number higher than 2048 has ever been discovered-and that is exactly half of the number recorded as produced at the Harper's Ferry Armory. There are between 200-300 of these pistols known to exist today.