A quick search, a new idea taking into account airmans "uncompleted midget sub" idea :
The visible part actually is only the pressure hull, that's why those circular windows are protruding, making the whole thing look like from the late 19th century, but the whole outer shell still is missing. As said by Raketyr, the photo stems from a book about German and Japanese midget subs, so the assumption, that it's German may be correct. Juding that "pressure hull", the bow may have been more pointed, as in other German midget subs.
The predecessor to the Biber was a single boat, called "Adam", which was built in 1944, and as stated in Fock's "Marinekleinkampfmittel" (Naval small battle units) got several modifications, before it transmuted into the Biber.
This photo may be shows the faired conning tower and the completed rear section.
In Gröner's "Die deutschen Kriegsschiffe 1815 - 1945, Bd.8.2", there's a drawing of the Adam:
The diving planes don't match the shape shown in the photo, neither do the torpedoes, but they may have been incomplete, too.
Just an idea ...