Absolutely do not swap out German-made VERBUS, KAMAX or other fasteners for modern Taiwanese made (C) or |0| headmarks. A little simichrome polish on an old t-shirt will work fine to bring the bolt head back.
That said, even new FACTORY bolts in Porsche packaging contain some Taiwan headmarks, including the ones above. They are in trivalent chromate coating, but they are the same as the ones you get at the hardware store. It's hit or miss-- I ordered a bunch of fasteners recently and came up with a few VERBUS and some Kamax in gorgeous black zinc.
Anyway, I like Sherwood's idea of replacing with new, then replating everything then putting it all back. . . sort of like painting the Mackinac bridge. Be sure to keep detailed notes of what came out of where. . . .
PS look what I picked up from the platers yesterday. . .
