Sorry, I still can't insert the links to the posted photos. I tried reversing the img tags and I get a red X with no link. I am doing something wrong..
I thought of multi format too but the film plane opening looks like a standard 2 1/4 size (no sign of adapter inserts) and the camera body is only 4 3/4 inches long. I would think that the body would be longer to support the larger formats.
My guess was that the older 120 film had frame number indicators in different locations.. depending on Manufacturer??