Patented by Alejandro Obregon in Mexico in 1934 and in the US in 1938, this pistol is an adaptation of the classic Browning 1911 to use a rotating barrel locking system. In addition, Obregon integrated a couple other clever elements. The safety lever and bolt stop were combined into a single part, in the process doing away with the need for the plunger tube on the side of the frame. The mainspring was made into a contain unit with the guide rod and spring plug, and a magazine safety was added through slight modification of the trigger bow and magazine catch.

Only about 800 of these pistols were made, at the Fabrica de Armas factory in Mexico City. It was not adopted by the Mexican military (which used the M1911A1), and was relegated to private sales only.