The manufacturer of the Magnetophone was what later became Telefunken.
The first paper tape used was covered with high grade ferric oxide barn
paint (rust red), and a cloud of red dust sprayed the air as the tape
was used.  It didn't have a long life, either.

3M did much of the research into long life acetate and later Mylar tape
with binders and lubricants.  I imagine that the abrasive ferric oxide
ate up recording heads rather rapidly.

Jim Cook