I have two very nice NOS 1968 mustang deluxe flip open gas caps.
1) Ford box is marked C8ZZ-9030-C. Gas cap has "sm" markings and engineering numbers C7ZA-9A107-B and C7ZA-9A112-B. No cam-on tether. $375
2) Ford box is marked F3ZZ-9030-A. Gas cap has "sm" markings and engineering numbers C7ZA-9A107-B and C7ZA-9A112-B. Replacement style with cam-on tether and installation instructions. $275
For pictures or more information, please contact me at brittonwhitworth@hotmail.com