My 70 CA built Challenger gas cap with the ECS system has the words PRESSURE VACUUM on the cap. That’s only for the cars with the ECS system. It in the FSM page 14-117. I think that cap is for any car w/o ECS. No idea of it’s value.
The pictured fuel filler cap is a Stant G-32E aftermarket replacement cap that fits several applications including the following:
1969 AMX
1964 - 1970 Buick, various
1964 - 1970 Cadillac, various
1964 - 1970 Chevrolet, various
1966 - 1970 Chrysler
1967 - 1970 Imperial
1965 - 1970 Dodge C-body and B-body, except station wagon
1965 - 1970 Plymouth C-body and B-body, except station wagon
1969 - 1970 Ford, various
1969 - 1970 Mercury, various
1964 - 1970 Oldsmobile, various
1965 - 1970 Pontiac, various
The part number is stamped on the cap.
It is not specified for a 1970 Challenger, but it will fit the filler neck of a non Evaporative Control System (ECS) tank, albeit a little loosely. When the tabs are fully engaged it will seal and hold. It is a non-vented cap for the non-ECS filler.
Pricing for the Stant G-32E is in the $15-$20 range for a new cap.