This is the earliest SunTour advert that I have. It depicts a SunTour 888 Wide pull-chain derailleur with the outer cable stop placed in the middle of the main arm. It appears to indicate that you can run 1/8” chain on 3 and 4 speed freewheels and 3/32” on 5 speed freewheesl - although I do not know if this is with different versions of the gear.
The paragraph at the bottom left seems to refer to the numbers 6, 8, 10, 12, 15 and 20, which are all multiples of 3, 4 and 5 rear cogs. Are these numbers of gears? Was there a fashion for triple and quadruple chainwheels at the time? I simply don’t know!