This U.S. Model 1842 was manufactured under contract to the U.S. Government in 1850 by Henry Aston in Middletown, Connecticut. It was the first percussion pistol issued to U.S. troops -- previous pistols had been flintlocks.
This pistol has proper inspector cartouches on the wood stock behind the lockplate -- JH (John Harris) and WAT (William Anderson Thornton). It also has "JH" (John Harris) proofmarks on the barrel and "H" on other metal components.