I just loaded an old Voigtländer Jubilar (early 30's) with a roll of Ilford 120 film. This only has markers for 6x6 frame numbers, so for every other picture you have to more or less guess how long to turn the winder.
Are there other makes of 120 film with 6x9 frame markers on the paper?
Do you have any ingenious ideas how to avoid overlap exposures when using film that only has 6x6 frame numbers?