The Dardick pistol was developed and marketed in the '50's, and looks like it.  It never made a big splash, but might have if it wasn't so ugly.  It used a unique bullet, called a 'tround', that encapsulated the bullet in a triangular sleeve.  This tround and the open cylinder arrangement allowed the pistol to be fed from a magazine in the butt, and not only that, but could conceivably be loaded while being fired!  (It would help if you had 3 hands.)  

Dardick advertising brochure

LifeSizePotato (what a name) is a collector of various unique guns, and the following video is a teaser for more in depth investigation into the Dardick to come.  He also has a post on SomethingAwful forums which describes the gun in great detail.  Very interesting gun that could have used the services of a visual designer, the likes of which presently work for Apple.