To help narrowing the window of time, I have a SJ donor door here with the data tag still on it, says it is off an S-code coupe with M13 scheduled build code (December 13,1966) and the vin is 7R01S15163*.
This places it EDIT: your example somewhere in later December I think, maybe Jeff has more data that narrows it more.
None the less, this seems to run consistant with the 2nd design early hood with wiring clips (not hoops) and grommets to prevent chafing of the wires (not rolled edges). It also has the braided wiring covers (not plastic) and the metal light sockets (not plastic).
I have learned so much here at Concours, I find out more every day!
1 happy mustanger!