Shimano had been slightly unenthusiastic about its pull-chain derailleurs in the 1950’s, and continued to be sceptical about parallelogram derailleurs in the 1960’s. But other Japanese manufacturers were piling into the market (Sanko and SunTour in 1963 and DNB in 1965) and so Shimano felt compelled to get involved.
I have been told that Shimano’s initial idea was that parallelogram derailleurs were best used as a way of widening the gear range available to users of hub-gears - and so they introduced the Shimano Combi 12 in 1965. Hiroshi Nakamura does not mention the Combi 12 but claims the first Shimano parallelogram model was the ‘3.3.3.’ and was introduced in 1965.
Everyone agrees that the next model was the Shimano Archery, closely followed by the Archery Wide and Archery-W. These were derailleurs that were clearly marketed to be used with multiple freewheels rather than with hub-gears. They demonstrate a pattern that is typical of Shimano - the leveraging of a single basic design to produce a plethora of slightly different models to appeal to slightly different market segments. Shimano are the kings of range extension, but have the rare knack of doing it logically and in a way that consumers can understand (not something you could say of, for example, Simplex).