The Model 1904 was basically the first working automatic pistol made by Webley (there was a 1903 toolroom experiment, but it didn't really work). Like all the Webley automatic that would follow, it was designed by William Whiting. The 1904 was the company's first effort at making a semiautomatic sidearm for the British military, so it was chambered for the .455 cartridge (a special rimless version made by Kynoch, after early experiments using the .455 rimmed revolver ammunition caused lots of problems stacking in magazines). It is a rather huge handgun, and uses a short recoil mechanism with two separate locking blocks. This particular one is s/n 23 - very few were made before it was rejected in military trials and Webley redirected its efforts toward smaller commercial pistols.