I purchased two Service Parts (351) Emblems C9ZZ-16637-C with attaching hardware in excellent condition. Each box contained 4 PAL nuts. The PAL nuts have been protected from the environment for ~53 - 43 years in vacuum sealed bags. As shown they have a "eggshell" zinc finish with the correct diameter flange. I expect they have dichromate finish on them. The sealer is rock hard.
I polished the 6 black looking OEM PAL nuts I have in possession with a buffing wheel and compound. The black finish was removed and a shiny zinc finish was exposed. I sprayed them with flat clear paint to match the service parts finish. I am very happy with the match. I did some internet research and found information that dichromate can turn a dark color when exposed to high temperature. Maybe this is the case? Alan