Here's a couple of pictures of a painted coil bracket. The bracket was put on the coil while the coil's marking was still wet and you can see the mirror image on the inside surface of the bracket. The bracket is painted a gloss (almost) black, the coil is painted a lesser gloss, more semi-gloss, the bolt/screw is, as Bob states, a soft silver as is the nut. Both were painted as well. The hex head bolt/screw has a "L" head marking. The date code is "5CBC" which I assume would be 1965, March, second week, 3rd shift (? on the last "C" for the shift). I assume this came from a San Jose built Mustang as most of the cars in the San Jose area were built in the San Jose plant (actually in Milpitas).
I can't answer for 1967 coils, but this one is painted and I'll continue to paint mine.
Jim