This is the opened Pattern 1874 McKeever Cartridge Box.

It holds twenty .45-70 cartridges for the M1873 Springfield Trapdoor single-shot rifle or carbine commonly issued to U.S. soldiers during the Indian Wars.

This Second Type, made about 1876-1878, had stiff varnished web loops to make it easy to extract cartridges. Releasing the top catch opens the case downward for quick and easy removal of the bullets. Not visible, stamped in leather, are the U.S. inspector's initials, C.H.