A most interesting vehicle for sure.
Even though I have pretty good references on both Brennabor and Gaubschat, I did not even get close on this one.
However, I do try to research these questions as thoroughly as possible and spent a lot of time looking at historical photos of the Wintergarten. Sadly, below is one of the photos I found.
Wintergarten at war's end, May 1945 under Russian eyes.
Bill