On a car of that vintage, I find it curious that such a decal is on the car. I was thinking the
normal "Air Conditioned by Air Temp" decals stopped being used after the 1968 model year?
The wording on the decal does sound more like an aftermarket AirTemp, dealer-installed unit, BUT all of those units were "hang-down" under-dash units rather than being fully-integrated into the instrument panel. By the time your car was built, seems like the use of the word "Air Temp" was only on the "Air Temp II" factory automatic a/c systems?
Any of the prior dealer-installed "Factory approved" a/c systems were usually more "aftermarket-look" as to many of the under-the-hood components, rather than the same items being specific-use oriented (lines, receiver/drier, condenser, and such).
Pictures of the under hood area and the instrument panel?
Just some thoughts and observations,
CBODY67