Quote Originally Posted by BradS View Post
Could it be 126 ? I remember 126 being the same width as 135 but square frame.
Correct, 126 film is 35mm wide, but can be distinguised by having a single perforation per frame, also preprinted numbers and borders on each frame. The negative size is slightly larger than 35mm, not having the usual 35mm perforations on both edges. (about 28mm square, compared with 24mm square for a Robot-type negative).