Fritz Fend worked for Messerschmitt on aircraft landing gear during the Vera Lynn War. After that he developed his Fend Flitzers, and when he wanted to increase production, he approached Willi Messerschmitt who decided to improve and mass produce the concept under the Messerschmitt name.
For 10 years after the war no German company was allowed to make aircraft, but when Messerschmitt was finally allowed back to plane making, Fend was allowed to continue production, and set up a new company called Fahrzeug Maschinenbau Regensberg which roughly translates as Regensberg Scooter-machine Factory, or more literally as Travel-Thing-Machine Factory, Regensberg.
Heinkel also produced scooters and bubblecars, and BMW, unable to produce aero engines concentrated on cars and motorcycles including building the ISO Isetta under licence. Sachs made the original 175 and 200 engines, and it is believed that Sachs and FMR collaborated on the design of the TG 500 type engines, but Sachs did not feel they were developed sufficiently to have their name on them.