M1917 revolver
The M1917 revolvers were six-shot, .45 ACP, large frame double action revolvers adopted by the United States Military in 1917, to supplement the standard M1911 pistol during World War I. There were two variations of the M1917, one made by Colt and the other by Smith & Wesson. They used moon clips to hold the cartridges in position, to facilitate reloading, and to aid in extraction, since revolvers had been designed to eject rimmed cartridges and .45 ACP rounds were rimless for use with the magazine-fed M1911.