[Stig Jarlevik]

Well Clint

Speculation again, but if you look at the reverse side of this post card it says Berlin Döberitz - Oberhof in Thür.

Just in case the producer is trying to tell us something, which just might be or indicate the crew are on a flight from Döberitz to Oberhof in Thüringen.
If that is what he is trying to say, I agree he would have been better off being a bit more explicit, but unfortunately this is all we got....

I don't think it was unusual for neither civilians to be allowed into military airfields nor military persons to fly (test?) civil aircraft from military facilities.

Just a theory anyway...

Cheers
Stig