Gosh....I have no idea. The 1920's-1940's Mercedes had the star as part of the radiator cap, but there would have been a rosette on the bottom of the star, and threads underneath to screw on to the radiator. I see no threads or sealing material (asbestos or brass) either. The shaft and base look home made to me, but I'm often wrong, so your guess is as good as mine.