The black item is the cartridge holder used in the Hoffer-Thompson .22 caliber version of the Model 1903 Springfield rifle. These were basically standard M1903 rifles, but with a .22 caliber bore. For the most benefit as training rifles for indoor gallery practice, they used these cartridge holders so the soldiers would be able to load the magazine from a stripper clip, and everything would be done exactly as with the service rifle and cartridge.
The spring and plunger/firing pin would be pushed back and a .22 short rimfire cartridge inserted into the slot in the holder, and then the holders would be loaded in the stripper clip and everything was ready for use. There was a special tool for ejecting the fired .22 short cases (basically a short rod with a wooden handle).
About 15,525 of the “Hoffer-Thompson” rifles were made at Springfield Armory between 1907 and 1918. They are fairly scarce, and the cartridge holders are getting much harder to find, with prices in the $35+ range on the few I have seen in recent years.
Thompson was John T. Thompson, an Army ordnance officer, best known for his later submachine guns.
The Hoffer-Thompson rifles were replaced, beginning in 1922 with a series of .22 caliber training rifles with sporter style stocks, and using a five round magazine and chambered for .22 long rifle caliber ammunition. Apparently there was greater desire to emphasize marksmanship and less need to duplicate the exact bolt manipulation and loading.