Sweet! I'm no expert but, it looks like you have a WWI M1912 "variant" holster to me. The hanger loop is riveted to the front and the leg strap holes are slotted versus rounded loops. Holds the Colt M-1911 .45. It is pictured on page 363 of Scott Meadow's book "U.S. MILITARY HOLSTERS AND PISTOL CARTRIDGE BOXES". I believe you have a nice rare and slightly valuable holster there.