U.S. Model 1836 flintlock pistol by A. Waters .54 caliber (AH8421)

NSN, made in 1840, .54 caliber, 8.5" round proofed barrel. Metal has been cleaned at some point, especially the hammer.  with mottled discoloration noted. Stock has two handsome cartouches visible with expected nicks and dings noted. Action holds at half and full cock. Lock plate is marked with "EAGLE/A.WATERS/ MILBURY.MS./1840. It is more than likely to have been issued in the Mexican American War.