Attached is 120 rollfilm filmback (it has "rollex-patent" printed on it. It is a rollfilm back for 6x9 plate cameras (you insert the rollfilm holder instead of sheet film holders...). It is for 6x9 images. I assume the polaroid will cover the frame almost completely.
To use polaroid film, I just remove the rollfilm back I put into it, and put the original back door on again.