here is the cap off of my mid-July '70 Challenger R/T

I believe it is the original - even has some "Earl Scheib GREEN" overspray on it

rubber seal to locking cap - no helper spring - blind roll pin at hinge & release (so it can't be seen from the top when mounted on a car) HOW TO REMOVE IT?

the "Locking Gas Cap w/Flip-Top" was the only OPTION, $4.40 in '70 ( not available separately ) & it was discontinued during the '71 model year