The Gerat 06H was the first fully roller-locker rifle,and the ancestor of all today’s roller-locked firearms (most notably the HK91 and clones). The 06H was a development of the Gerat 06, which was roller locked and gas operated. Mauser engineers determined that with special attention paid to part geometry, the gas piston of the Gerat 06 could be left out entirely, and the roller system could function as a delayed blowback action. This made for an extremely simple (and inexpensive) design. The body of the weapon was also designed for cheap manufacture, being made of metal stampings and as few machined parts as possible.
The Gerat 06H was chambered for the German 7.92×33 cartridge, and used the same magazines as the mass-produced StG44. The 06H would eventually be adopted as the StG45 and was intended to replace the StG44, but the war ended before more than a few could be produced. The designer engineers continued their work in Spain after WWII (producing the CETME rifle) before returning to Germany in the employ of Heckler & Koch.
Very few of these rifles were built, and the one we have photos of here is unfortunately incomplete.