Colt 1911 Frame

Click on image to enlarge - Use back button to return

Unknown 1917 era Colt 1911 Frame with a receiver for a rifle barrel and the firing pin is positioned for a rimfire cartridge. It also is equipped with two vertical uprights at the top of the receiver and a gas escape port on the right left side. The grip safety has been replaced with a solid backstrap/mainspring housing. The half slide may not be original to the frame. Any ideas?