I present to you, the most photographed film holder on earth!
Seriously, though, what does this fit? Width 100 mm, length 150 mm up to the insertion point of the darkslide, thickness 4 mm. The lip on the lower part of the holder is 9 mm long. Otherwise, I guess the photos says it all.
Is this what is known as Universalfalz? The holder takes 9x12 cm film.