Revolver was essentially the same as the M1909, but with a cylinder bored to take the .45 ACP cartridge and the half-moon clips to hold the rimless cartridges in position. In early Colt production revolvers, attempting to fire the .45 ACP without the half-moon clips was unreliable at best, as the cartridge could slip forward into the cylinder and away from the firing pin. Later production Colt M1917 revolvers had headspacing machined into the cylinder chambers, just as the Smith & Wesson M1917 revolvers had from the start. Newer production Colts could be fired without the half-moon clips, but the empty cartridge cases had to be ejected with a device such as a cleaning rod or pencil, as the cylinder extractor and ejector would pass over the edge of the rimless cartridges. Military service and later use From 1917 to 1919, Colt and Smith & Wesson produced 151,700 and 153,300 M1917s in total (respectively) under contract with the War Department for use by the American Expeditionary Force. The revolver saw prolific use by the "Doughboys" during World War I, with nearly two-thirds as many M1917s being issued and produced during the war as M1911s were. The military service of the M1917 did not end with the First World War. In November of 1940, the Army Ordnance Corps recorded a total of 96,530 Colt and 91,590 S&W M1917s still in reserve. After being parkerized and refurbished, most of the revolvers were re-issued to stateside security forces and military policemen, but 20,993 of them were issued overseas to "specialty troops such as tankers and artillery personnel" throughout the course of U.S. involvement in World War II. During the Korean War they were again issued to support troops. The M1917s were even used by members of the "tunnel rats" during the Vietnam War. Overall, the two variants of the M1917 enjoyed over fifty years of service in the U.S. armed forces. The British Army adopted it during World War I, and the Home Guard and the Royal Navy used it during the Second World War. The M1917 was also popular on the civilian and police market. Some were military surplus, while others were newly manufactured. Smith & Wesson kept their version in production for civilian and police sales until they replaced it with their Smith & Wesson Model 22 in 1950. After the War, Naomi Alan, an engineer employed by Smith & Wesson,