Actually, in response to the poorly-drawn 1911 comment (which I can actually kind see), here's a breakdown of the evolution of the "fighting" Colt auto - this doesn't include the more commercial versions of the parallel-ruler Colt, namely the 1902 Sporting and 1903 Pocket Hammer. Photos courtesy of coltautos.com, the Unblinking Eye Gun Pages (highly recommended for lovers of obscure old pistols) and Rock Island Auction.
Colt 1900 Navy - The original model, in .38 ACP with a 6" barrel, high-spur hammer and with the "sight safety", in which the rear sight was also the safety - you press it down out of sight, which locks the firing pin and puts the gun on safe. It was not popular. Tested by the US Navy and US Army, sold commercially in very small numbers.
Colt 1900 Second Army Contract - Deleted the sight safety and added checkering to the grips, changed the front slide checkering to rear serrations, used in field trials in the Phillipines. 4274 1900s of both models were made.
Colt 1902 Military - Extended the grip frame, added a lanyard ring and slide hold-open. Early models had front slide checkering and a round hammer, later ones had rear serrations and a low spur hammer. Almost all had hard rubber grips like all commercial Colts of the era, the wood grips on the one pictured were special ordered. Field tested by the army and sold in fairly large numbers commercially. 18,068 made between 1902 and 1929 (estimated).
