If no specifics what was the norm for Dearborn car on coating for rear bumper bolts?
That was the challenge since it appeared that there was no "norm" across such a long period of time
Late July early Aug. 1964?
We can work with that
Looks to be zinc plated washers - phosphate and oil bolts
From just before that period 5F07F190941. Baked by the strong sun for along time has effected the look of what finish is left but you can tell that there were different finishes
And from right after that period (one of Mike Murray's unrestored cars) 5F07A2706xx
Sure you noticed two different sized washers being used. Appears to be allot of running changes on these parts during the first year