Colt M1917 revolver
Colt had produced a revolver for the U.S. Army called the M1909, a version of their heavy-frame, .45-caliber, New Service model in .45 M1909, a version of the .45 Long Colt with an enlarged rim to facilitate extraction, to supplement and replace a range of 1890s-era .38 caliber Colt and Smith & Wesson revolvers that had demonstrated inadequate stopping power during the Philippine–American War. The Colt M1917 Revolver was a New Service with a cylinder bored to take the .45 ACP cartridge and the half-moon clips to hold the rimless cartridges in position. Later production Colt M1917 revolvers had headspacing machined into the cylinder chambers, just as the Smith & Wesson M1917 revolvers had from the start. Newer Colt production 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 rims of the rimless cartridges.
During its lifetime, the Colt New Service was the most popular revolver made by Colt, surpassing 150,000 units. After World War I, the revolver gained a strong following among civilian shooters.
John Henry Fitzgerald was an employee of Colt prior to World War II and was known to carry of a pair of New Service "Fitz Specials" in his front pockets. These revolvers had bobbed hammers, 2" barrels, shortened and rounded grip frames, and the front of the trigger guard was removed. Although less than 30 left the factory, it became an after-market conversion for many gunsmiths. Colonels Rex Applegate and Charles Askins were proponents of this model.
Canada and United Kingdom
In 1899 Canada acquired a number of New Service revolvers (chambered in .45 Colt) for Boer War service, to supplement its existing Model 1878 Colt Double Action revolvers in the same caliber. In 1904/5 the North-West Mounted Police in Canada also adopted the Colt New Service to replace the less-than satisfactory Enfield Mk II revolver in service since 1882.
New Service revolvers, designated as Pistol, Colt, .455-inch 5.5-inch barrel Mk. I, chambered for the .455 Webley cartridge were acquired for issue as "substitute standard" by the British War Department during World War I. British Empire Colt New Service Revolvers were stamped "NEW SERVICE .455 ELEY" on the barrel, to differentiate them from the .45 Colt versions used by the US (and Canada).
The Colt New Service was a popular revolver with British officers, and many of them had privately purchased their own Colt New Service revolvers in the years prior to World War I as an alternative to the standard-issue Webley Revolver. 60,000 Colt New Service revolvers were supplied to British Empire and Canadian forces during World War I, and they continued to see official service with US until the end of World War II.