Dave, What you posted was the "BaseBall Diamond" stamp picture that I took a few years ago. That stamp is the "FINAL OK" stamp for '65-'66 Dearborn cars only, and is seldom seen. It is not the "PAINT OK" stamp for '65-'66 Dearborn cars. These "BaseBall Diamond" stamps were actually first used (with different numbers) on the '55 thru '57 T-birds. The correct stamp is below, and is usually found on the cowl from the middle to the passenger side of the cowl, but as I said, seldom seen.
'65-'66 "Paint OK" for Dearborn Plant
Here is the '65-'66 "Paint OK" stamp for Metuchen, NJ cars. Note that the assembly line workers name is also attached. I'm sure that the named varied..lol... such as MARTZ, PAYNE, etc. This guy's first or last name was SASWAY. *Have also seen a few of these stamps below found on the right side inner shock tower also for Metuchen.
'65-'66 San Jose "Paint OK"
Charles has a pic of one from his recent '65 K Code vert restoration.
Maybe someone can post some '69-'70 year "Paint OK" stamps as the original poster requested.
Tony K.