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NOT MINE!! Seen on FB, these may be available.
The Black one is for auto temp, came out in '68 with the introduction of the auto temp system.
The Blue one was for auto temp ll, not sure about the exact date but I think it was 1974.
These were usually mounted on a roll away console with some other test equipment. Both were pretty much useless for finding the large number of small vacuum leaks that plagued both systems.
I agree the black one is for the first version of Auto Temp. The blue one is for Auto Temp II for the years 1971-73. I do not believe the blue one will work for the Auto Temp II systems for 1974+. I can verify that the blue tester is useful for the version II systems 1971-3.
The blue one might be useful down the road for Wyatt given that @ayilar has at least one of those cars...........
You are probably right, I remember using the blue tester, but after this many years I can't remember what years it worked on.