Six companies were asked to design prototypes. These were: Gustloff-Werke, Mauser, Johannes Großfuß Metall- und Lackierwarenfabrik, C.G. Hänel, Rheinmetall-Borsig and Heinrich Krieghoff Waffenfabrik. Several contracts were given out, but only a few prototypes are known to have been given. Mauser gave a version of the MG 81. However, it was turned down because it was too heavy and got its bullets from a belt. There was one design, made by Louis Stange at Rheinmetall-Borsig, that was accepted. It was tested at a test station at Tarnewitz in mid-1942. This prototype was called Gerät" 450 ("device 450") or Ausführung" "A" ("type A"). It was supposed to be a sheet metal design. The type "A" was never made (except for some models). However, the basic design was kept for more development.