B-17 Identification after crash

Hi there,

this is my first post here and I have just one question.
I am working a long time looking after plane crashes in the region around Magdeburg (Germany), German and Allied.
Now I have received a photo of a B-17 Wreck, whose identification is difficult.
Nothing is known of this photo - no date, no place, no markings to see, but must be in the vicinity of Magdeburg.
Here you can see the rear fuselage floor with the cutout for the ball turret and the level/stair for the radio room.
Oddly enough, the cutout for the ball turret is closed, but why?
Also interesting is the tube on the right side - that looks like a toilet - what is this?
can anyone identify the version of this wreck? B-17 x-xxx?

Thank you very much
Greetings from Germany
Andreas