This rifle was produced for the mid-shipmen at the Naval academy in Annapolis. Only 498 of them manufactured.  Richard Hosmer indicates these rifles remained in service at the Academy until 1890. Chambered .50-45 this is a slightly smaller scale rifle which has a more slender butt stock. It balances well and is a pleasure to handle.  The Navy preferred the stud extractor located in the bottom of the concave hub breech block, one of the critical identifying features of this rifle. The receiver has a screw normally present to retain the straight bar extractor. However, in this model rifle, the screw serves only to fill (plug) the hole.  The receiver is marked with an anchor on one side while the other side has the P over FCW inspectors initials (Frank C Warner). The rear sight is from the Springfield Armory where these rifles were assembled.  The rifles saw a lot of service and many of them are less than pristine.  With only 498 manufactured a complete unaltered example of this one is a real find.  The serial number (along with a U.S.) is located on the top of the butt plate. Photos of a rifle from my library.