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 "JAS.H.MERRILL/BALTO.PATENTED/JULY, 1858." (double stamped), and the top of the barrel at the breech is marked "Wm JENKS" parallel to the bore ahead of "USN/RC/P/1845". Two inspection cartouches stamped on the left of the stock opposite the lock (one obstructed).

Fine, retaining 60% period refinished brown finish on the barrel with some areas of light fading. Case colored lock and breech lever turned to a smooth gray patina. The refinished hammer has a reattached replacement top section. The brass fittings exhibit a mix of golden bright and golden aged patinas. The stock is also fine as re-oiled, with numerous scattered mild dents and scratches, one obstructed cartouche and the other cartouche defined. Mechanically fine.