It is certainly not U.S. All U.S. made Remingtons used pins for the hammer and breech block, retained by a single plate held on by a screw.
It is a Model 1867 Norwegian/Swedish rifle. Norway and Sweden were one country from 1814 to 1905, and that rifle was made in both areas (now countries). Rifles were built in Norway by Kongsberg Vapenfabrikk and Hovedarsenalet in Oslo (then Christiana) and in Sweden by Husqvarna Vapenfabrik. AFAIK, only those Scandanavian makers replaced the pins with screws, and added capture screws (like those on some Mauser trigger guard screws) to keep the large screws from turning.
All those military rifles, though, had a plentitude of markings - numbers, letters and crowns galore. But many were converted to sporters in both countries and some in the U.S. and it is possible that markings were removed in the process. It is also possible that some sporters were made which did not have the military markings, but I would think they would at least have a maker's name.