Mexican Obregon 11.43mm (.45ACP) Pistol with an original holster.
A few (800 - 1,000) were manufactured at the National Arms Factory (Fabrica Nacional de Armas Mexico) in Mexico City during the 1934 - 1938 time period. The pistol was designed by Alejandro Obregon and a Mexican Patent obtained in 1934, with a U.S. Patent issued in 1938. It differs from the Colt 1911 design by having a rotating barrel.

Another example - New in an original box!