Frankford Arsenal already started development of a military automatic pistol cartridge during 1904 with commercial cases manufactured by Winchester. In 1905 Frankford Arsenal was requested to develop a quantity of cartridges for testing in early 1906. A rimless and semi-rimmed case was developed but before production could start on either the ordnance Board decided on the rimless design. This round was called the Model of 1906 Cal. .45 Automatic Pistol Ball Cartridge. This is the excellent article about the development history of the 45 Automatic (Erlmeier, Brandt Ref. 427).