In late 80's I was working part time in BMW motorcycle shop in Md. Elderly guy walked in wanting to sell a BMW single cyl that he bought after WWII while going to college. I went to his house to pick it up and he pulled the key out which had a swastika on it and replaced it with original, identical but for the swastika. His story was while flying a B25 during Normandy invasion he took hits in engine/s and managed to put it down in field. Told crew to spread out. While in trees he heard big motor rumbling as tho idling. After watching the German tank for a bit he realized it had been abandoned so he climbed inside, saw the ignition switch, pulled it out and stuck it in his pocket. It was identical to later ones used on BMW cycles for many years, minus the swastika of course.