The legend goes that Shimano produced a ‘racing’ pull-chain derailleur called the ‘3.3.3.’ in 1956 and a ‘touring’ pull-chain derailleur called the ‘Champion Speed’ in 1957.
My guess is that this is the Champion Speed. The pulley cage, sliding rod and spring assembly are the same as on my other Shimano pull-chain derailleur - the difference is the chainstay mounting. I am not sure that a derailleur with such a short cage would have been that suitable for touring wherever it was mounted. I suspect that Suntour understood touring better at this time.
This is a competently manufactured component but does not have the class of either the Sanko or the SunTour pull-chain derailleurs. Shimano’s real interest clearly lay elsewhere - with their 1958 ‘3.3.3.’ three speed hub gear.
Browse associated documents.