Bosch produced a number of components, the famous starter magnet [also produced for trucks] (contrary to common belief with German planes the propeller was swung to prime the engine and then started by cranking the starter magnet) The switches came in different versions for one and two magnets. [careful here the switches for cars are very similar and were produced throughout the 20s. Lastly there are also two pictures of the actual magnet ZH6. [similar to car magnets too]