Sanitaire Blue Line Series Introduction?

[kirbyclassiciii]

May I ask if anybody here remembers exactly what year Sanitaire's "Blue Line" series of consumer-use vacuum cleaners came out?

I want to think it was 1983, which was the year they had their canned-ham canister model S440A. The first few uprights in the Blue Line were models S639 (same as commercial SC679 "Maid-Saver"), S644 (SC684), S646 (SC686) and S648 (SC688).

~Ben