The bottom piece is labeled as a “US Remington 1917 Rifle”. While it certainly was built by Remington in the United States in 1917, it is a Russian M1891 Mosin-Nagant, intended for the Czar’s armies fighting the Boche. Several technical problems interfered with delivery, however, such as Russia not paying, then chickening out of the war, then falling to fighting amongst themselves in November of that year. Pretty much the only Remington-built Mosins to ever see Mother Russia arrived there postwar in the hands of US doughboys who used them to shoot at Bolsheviks (which is a fine and good thing to do with a rifle.)
Read the whole thing, as they say.