Hi Gerd:
I owe you a public, personal apology for this quiz and I am doing so now on this post.
Not to write a book, but often I have a go at a puzzle and if I am not making progress I sort of leave it and see how it develops. With other puzzles, I think I am on the right track and I go after it like a dog with a new bone. Such was the case with this car.
I have spent maybe six hours on this quiz, using not only my reference library here at the house but spending also hours on the internet using every matrix combination of words/names/dates/places etc, I could think of. Google.us/Google.de/Google.at/Google.fr etc. etc.
After visiting every Zündapp site I could find in all of this and finding absolutely nothing, I became convinced that it was what I said a few days ago, an NSU, as I had found numerous vehicles that came very close to the quiz photo. I then "called you out" as we say here and suggested you may have posted the wrong photo.
That turns out to be totally incorrect on my part and I apologize for my remarks.
I will be more careful in the future.
Bill
