Kahrmann in Fulda? Did he build Motorcycles? (Edit: Ok, now that I saw the plaque, I get it. No, that shop doesn't exist anymore. Motorcycles pretty much died out in the fifties and sixties in Germany and resurged only in the seventies. Even I had one then. The eighties were their heyday, since then sales have gone back again, but not as badly as in the fifties and sixties.)
I only know of a Karmann in Osnabrück who customized Volkswagens back in the day:
The U-Boat bike could be an NSU alright:
I venture to guess that this bike wasn't at American shores in 1938 already but was probably traded in for a couple of packs of Lucky Strikes and some canned fruit between 1945-48! American GIs hardly ever had to resort to plunder or rape, they always had something desirable to bargain with and if it was attractive muscle mass and good skin and teeth due to US Army rations.
