I have something very similar but mine predates the model 1917. Mine is the S&W .455 Hand Ejector originally intended for the civilian market as the Triple lock model and chambered in .44 Special these were converted to fill an order for the British military and rechambered for the British .455 Eley cartridge. Beginning production in 1914 these were the first of the S&W N frame series. The first run featured the fully shrouded ejector rod of the triple lock, this was eliminated in the second and third runs. Mine was made sometime in 1915 or 1916, shipped to Britain and eventually issued to Canadian forces eventually mine found its way back to the US and probably sometime in the 1950's was rechambered for .45 Colt.