This is most likely a transitional model second pattern Merrill cavalry carbine that is distinguished by the serial number at the back of the lock. It was made without the patch box. The lock is marked "J.H.MERRILL BALTO / PAT JULY 1858, / APL.9. MAY 21-28-61". The left side of the stock above the saddle ring bar has a oval unreadable cartouche. The left side of the barrel next to the rear sight is marked with a "V / P / eagle head" proof. Blade front and three leaf rear sight. Brass barrel band, trigger guard and buttplate, fitted on a one piece straight grip stock with a saddle ring bar and ring mounted on the left side flat. Merrill carbines were issued to cavalry regiments in New York, Pennsylvania, Delaware, Wisconsin and Indiana.