Hello Markus and welcome to the forum
Very nice collection you have there
I actually have a 411.120, so the Westfalia 411, rather than the 401. I did know where there was a frog eye 401 once but when I contacted the owner to see what they wanted for it, they never got back to me.
Sadly my Westfalia will soon be up for sale, as I just don't have the time to finish it, and I have my eyes on a much easier, less time consuming daily driver project. It will sadden me to see it go, I take great pride in owning it, but I'd much rather see it go to someone who will finish it and look after it, than to see it sat where it is.
Cheers, Brian