That beautiful golden finish, with hues of red, green and blue...
That's yellow zinc chromate, the attractive, protective plating/coating that covers new nuts, bolts, brackets, etc. and once graced the bits on your classic (or newer) car. The trouble faced by the restorer is that many of these pieces are either very expensive or no longer available.
Your old parts can be stripped down to bare steel and refinished to look like new, with the long-lasting protection zinc plating provides. The chromate adds a layer of additional protection. I like it because it just looks "right". Paint-on coatings don't quite do justice to a proper restoration or engine bay refresh.
I specialize in working with old, rusty parts from collectible and/or beloved cars. I'll answer your questions personally. I plate in small batches, one order at a time, so there's no chance your parts will get lost or misplaced. Unlike large-volume commercial platers, I'll do all of the prep work.
Yellow zinc-plated (also known as "zinc iridite" parts are used by Audi, BMW, Porsche, Jaguar, VW, Alfa Romeo, Saab, Opel, Ferrari, Mercedes and countless other car makers. Many older cars had yellow or "gold" cadmium plating, which looks more or less the same as zinc.
The above part is part of a batch of original pieces we restored for a 30 year Mini Cooper....like new again!