Only an estimated 300 Jenks carbines were altered by James H. Merrill to the Merrill system for the U.S. Navy in the late 1850s to 1860 in order to test the practicality of the Merrill combustible paper cartridge as opposed to William Jenks' system, which required loading with loose powder and ball. It has a blade front sight on the upper barrel band, and combination folding leaf rear sight graduated up to 500 yards with its base acting as a catch for the front of the breech lever. The breech lever has the two-line marking "J.H. MERRILL BALTO/PAT. JULY, 1858.", the lock is marked "N.P. AMES/SPRINGFIELD/MASS." behind the hammer, and the top of the barrel at the breech is marked "Wm JENKS/USN/RP/P/1845".

Fine, retaining 40% thinning original brown finish on the barrel with some light scratches and handling marks. Case colored lock and breech lever showing patterns of muted case colors with the balance mostly turned to a gray patina. Pleasing original aged patina on the brass. Stock is very good with some scattered dents, scuffs, scratches and chips with an otherwise attractive original oil finish. Mechanically fine.