Pat,
You are correct sir. It was from either LATE 1977, when the blue colored line was "formally" introduced, to "sometime" during 1978. I guess I should have made it more clear to the people who may need actual facts.
I'm going by the information that was supplied by the current Sears catalog(s) of the time. While I have no "proper" 1978 S/S or F/W catalog for 1978, I do have a 1977 Fall and Winter that introduces the blue models with NO Solid State controls, and 1979 Spring and Summer version that do make it quite conceivable that during the 1978 run, and with the pictures supplied above, surely attests that the new reset button, and Solid State mechanism was introduced formally during that year, 1978.
I do not have actual production dates, and I think no one else does either. This in mind, would "possibly" mean that you had an early series Kenmore form the 1977-1978 model run, including the non-Solid State PowerMate on your cleaner. The reset, with the Solid State" electronics was new during that period tho, as no previous green version ever had it either. Neither of my nozzles do and I have an Early nozzle, and a late one to that series. Yet clearly it was introduced at "some" point as the one found above has it.
Yet prominently featured in the advertising of the 1979 Beige models with the woodgrain and orange trim, was the new Solid State Controls on the PowerMate. This of course was after the introduction of this series that would be concurrent with the 1978-79 Fall and Winter catalog...
Enough confusion for you?
Chad