Hi Ian , you study Kanji , that is a great thing. If I were you , I would not have had that motivation for additional new language 😅
The emissions decal , that is a part two of emissions programs of the Japanese government.
The part one was January 1973 , all cars needed to reduce 3 degrees of ignition timing .
The part two was February 1973 , all cars had to have the green ball to reduce the ignition timing.
The part three was March 1973 , almost all cars had to have new carbs , canisters, reservoir fuel tank etc at assembly lines ( S20 cars didn’t) .
After March 1973 , when at a periodical maintenance and a Shaken inspection ( required by the government) , all cars had to have the green ball even if the car was made before January 1973 .
My Fairlady 240ZG still has the green ball , but I can’t feel loss of enjoyment. My Z432 , I didn’t want it so get rid of it . Today at the required inspection, the green ball doesn’t have to be there , I don’t know why . Maybe it was a recommendation?
Kats