Thanks Norbert,
in regard to the glider school at Köthen and the dislocation of Schleppgruppe 1 during winter 44/45 this is a very good clue. Just now I see what could be a towing device aft of the tail wheel.
So what we have here would be a tankbuster retrofitted as a glider tug - I only have seen B- and D-variants modified this way, so this seems to be a really interesting photo after all...
Thanks again,
Christian