[geunther]

DM were (I believe) zink dichromate (referred to also as cad,gold with other colors rainbowed in). Bendix were black.

I am not affiliated but I am using Mike at brakebooster.com. Seems easy to work with and called me to warn me that there was fluid inside my booster. He was essentially warning me about a potential problem with my MC. I was aware of the previous leak and had already rebuilt it, but I was impressed that he thought to call and advise me.

If nothing else, his site shows the various plating finishes. Image is from the site.