The 455 Webley was the official side-arm of British troops during the outbreak of the First World War in 1914, but after hostilities ceased, the military decided that in a modern era a lighter revolver would be sufficient. The firm of Webley & Scott submitted their revolver design in November 1921 to the British Small Arms Committee using the 38 Smith & Wesson cartridge that was designed by S&W in 1877 for their Baby Russian revolver. Although there were concerns about stopping power, trials were conducted at the British School of Musketry with a 200gr round nosed lead bullet with encouraging results. Further trials comparing the 380 Revolver against the .455-caliber continued through 1927 and the “CARTRIDGE SA BALL REVOLVER .380-inch MARK 1” and “CARTRIDGE SA BALL REVOLVER .380 inch MARK 1z” was approved for service in November 1930. (Erlmeier, Brandt Ref. 376)

The standard design of the Mark 1 was a 200-grain round-nosed lead bullet. Even before the War, concerns were raised about the use of lead bullet designs and whether it was in contravention of the Hague Convention and in 1936 trials were conducted with jacketed bullets. The Mark 1z was declared obsolete in October 1934 and the Mark 1 in June 1938.

The drill round was designated “CARTRIDGE SA DRILL REVOLVER .380 INCH D MARK 1” in June 1934. Blank loads were used, the specimen above has a headstamp KYNOCH  38 – 200. The 380 Mk. 1 was also made in the US and was known there as the .38 S&W Super Police.