There are very little notes that survived regarding this cartridge, but the best available info can be found on p.290 of Labbets’s “BRITISH SMALL ARMS AMMUNITION 1964 – 1938.” It appears to have been developed around 1901 and is a semi-rimmed cartridge. There also exists a rimmed cartridge called the .500 Kings Norton Colt Experimental. The .500 Colt Kynoch was also referred to as the .500 North, with North referring to a Mr. T.K North, who was employed by Colt in London and who held a number of patents regarding machine gun designs.