The standard American military sidearm was officially adopted in March 1911. In the early 1920s, the design evolved into the 1911A1 model. Key modifications included an extended hammer spur, an elongated tang on the safety, a slightly longer trigger with a relief cut for the trigger finger, an expanded front sight and an arched mainspring housing. All components are interchangeable. During wartime, manufacturing contracts were awarded to Caron Brothers (Canada), North American Arms Co. (Canada), Singer Sewing Machine, Union Switch and Signal, Ithaca Gun Co., Colt and Remington Rand. Remington Rand emerged as the largest producer, manufacturing over a million units between 1942 and 1945. Civilian market production featured a serial number prefixed with a C. In 1933, a variant known as the national match was introduced, characterized by hand-fitted components, tighter tolerances and adjustable sights. This model was discontinued during World War II but was reintroduced in 1957 as the Gold Cup model. In 1949, a model with an alloy receiver, known as the Commander, was launched. It featured a barrel that was 3/4 inches shorter and a rounded hollow hammer. All models utilize the same magazines, which are also compatible with Argentine, Chinese and American replicas.