This has an USN 1845 lock and the barrel is USN 1845 RP over P. There is an inspector Cartouche on the left wood. The mechanical function is very good crisp and tight. The 6” barrel is a 54-caliber smooth bore and does have some fine pitting. Overall, this Navy pistol is very good condition. They were used early in the Civil War till the Navy and Army were up graded with percussion revolvers.