The 20mm and 38mm Zuikos which were made with auto diaphragms and in OM mount still did not have their own focusing helicoids. There seems to be some misunderstanding concerning Kino Precision, the maker of Kiron lenses and Vivitar. Some Vivitar lenses were made by Kino and some weren't. The 55/2.8 macro and 90/2.8 macro Vivitars were made by Komine (28XXX...). The 90/2.5 Series 1 was made by Tokina (37XXX...). I read that there were prototypes of this lens made by Kino and with the 22XXX... serial number but haven't seen any of them or even photos of them. They may have been sold outside of the U.S. The 100/2.8 and 105/2.5 Series one Vivitars were made by Kino (22XXX...). Vivitar may have used some poetic license with the marked f/stop on the 105. The only one of these I don't have is the 105 Series 1.