Three companies were asked to submit designs: Metall und Lackierwarenfabrik Johannes Großfuß AG of Döbeln, Rheinmetall-Borsig of Sömmerda, and Stübgen of Erfurt. Of the number of proposals submitted, Großfuß AG's proved to be the best design by far, employing a unique recoil-operated roller locking mechanism whereas the two competing designs used a gas-actuated system. Interestingly, the company had no earlier experience in weapons manufacture, specializing in pressed and stamped steel components (the company's staple product was sheet metal lanterns). Dr.-Ing. Werner Gruner, one of the leading design engineers with Großfuß, knew nothing about machine guns when he was given the task of being involved with the project, although he specialized in the technology of mass production. Gruner would attend an army machine gunner's course to familiarize himself with the utility and characteristics of such a weapon, also seeking input from soldiers. He then recycled an existing Mauser-developed operating system and incorporated features from his experiences with army machine gunners and lessons learned during the early stages of the war. ~~Being made out of stamped metal, the new design required considerably less tooling and was much simpler to build than other machine guns—it took 75 man hours to complete the new gun as opposed to 150 man hours for the MG 34 (a 50% reduction), and cost 250 RM as opposed to 327 RM (a 24% reduction).~~