Why do you say it's a HX registered as a HZ? What was the month and year of manufacture?

>9/77 is HZ <8/77 is HX

Super Mint (not suppermint) is a 1977-8 colour. It should read 1938 on the trim code and 567-30529 on the paint line of the tag.

Someone else should be able to fill you in on the standard stripe colour for Super Mint.