@talk72000,
... and you certainly know the "Rundschreiben" ('legal letter')to this law, which verifies it and extends it to "Zigeuner, Neger und ihre Bastarde".
However - all that isn't my point.
I'd thought the question was that Germans in those years were asked to prove their
Germanic backgrond - something certainly couldn't be done by a motor car club's membership (at least not in 1935).