If you are going to post pictures, start a new thread in the Parts section and title it "Bolt Head Markings, 64-66". Please include where the bolts are located (fender, hood, etc), the VIN or at least the plant and build date. This is a project that has generated interest but no action and maybe it's time to do something about it. Other year cars, start another thread with a title of "Bolt Head Marking, 67-68", "Bolt Head Marking, 69-70" "Bolt Head Marking, 71-73" or "Bolt Head Marking, Other Ford Products" (Cougar, Fairlane, etc).
Jim