This subject was discussed on another forum in relation to Treblinka.
I was told by another poster than the "bone crusher" at Janowska was moved to the extermination camps to crush the bones.
He said this machine is a ball mill.
A ball mill could be used to crushing bones or anything hard.
The photographs of this machine get banded about a lot.
A poster stated it was a trommel - a screening machine as mentioned here.
I dug out a photograph of a modern trommel which another poster here has posted.
It you look closely at the screen it has the ripple iridescent you see on the surface of a curved slightly rippled mesh.
It is clearer here on an enlarged view I made.
Look more closely and there appears to be another cylinder inside the outer cylinder which you can see through the mesh, further evidence it is a mesh.
I have outlined the inner cylinder.
A modern trommel looks like this.
It would be really cool if we could get the make and model of this thing along with the catalogue from the manufacturer.
That would crush the idea this is a bone crusher (or not depending on what it turned up)