In their adverts from 1968 and 1969 Vista are using the Huret Allvit gear. In their 1972 advert they appear to be using SunTour gear levers paired with a Huret Allvit derailleur. But in this 1973 advert they are clearly using the SunTour V GT, probably branded up as a Vista V GT.
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Vista V GT 1972?