This question could have been answered rapidly thirty years ago when Hubert Nerwin was still alive, as he was both the father of the Super Ikonta line and also most accessible. As so often happens, though, the question did not arise until he had shuffled off this mortal coil.
It is my understanding that there were significant variations in film thickness and backings on the early B2 (120) emulsions, so Zeiss Ikon just took a conservative position and chose 11 exposures to ensure that there was less chance of the first or last frames being light struck as you have one additional roll of film at each end -- the Super Ikonta has a longer leader at front and back.
By the time the BX was introduced two years later, industrial standards for B2 film had become more reliable, so the BX was set to take 12 exposures. I suspect that this would have been adopted on the Super Ikonta III planned for 1943 had the War not intervened.
It really is not much of an issue in the end. Marc msmall@xxxxxxxxxxxx Cha robh bàs fir gun ghràs fir! --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org - Online, searchable archives are available at //www.freelists.org/archives/rollei_list
