At the time this camera was introduced (1938 or so) not all 120 film was long enough to get 12 frames of 6x6 when starting with the 6x9 frame 1 mark -- which was done because not all 120 film had 6x6 frame markings before the War, either. Post-War production changes would have required changing the machinery that (precision) cut the notches in the wheel, which wasn't a good use of resources while still rebuilding from the War and Soviet confiscation of at least one of their production facilities as war reparations. This while work was already underway to produce the Super Ikonta III which, among other things, eliminated the precision prism fitting in the rangefinder extension on the front standard in favor of a rangefinder that worked the way almost every non-Zeiss rangefinder camera did.