On page 19 of this issue, which arrived recently in my mailbox, a person named John Smith of Big Redd in Worcester UK
https://www.biggred.co.uk discusses the brake calipers on "older Mercedes" without further elaboration as to model of Mercedes, or kind of brake (Girling or ATE, for example).
The sidebar says, "If you enter your Mercedes in a Concours event, the calipers would need to be electroplated because the judges will be marking them on originality."
In the text of the article, he states, paraphrased, that when new the calipers will have had "an electroplated finish...this looked like gold in the 1960s...silver in the 1970s..." I note with curiosity he doesn't mention whether cadmium, zinc or other plating. Just color.
It's probably no surprise that Big Redd is in the brake caliper restoration business. They offer electroplating services (though they farm that out; they do the caliper rebuild, not the refinish) he warns that if going the electroplate route, you need to have them "copper coated" at an additional cost of £150.
As I have only seen nasty originals (unrestored and many years old) as well as restorations done here in the USA, I can honestly say I've never seen a Pagoda with plated calipers. So, what's the deal? Anyone seen a Pagoda when new? Were our calipers plated?
FWIW, when I restored my car I sent my calipers out for rebuild locally. They came back looking pretty new, but with the caliper body being left as raw cast iron. I found this material called Calyx manifold dressing, which is basically a graphite grease that you rub into the raw cast iron. It lasts a very long time on brake calipers, not so much on manifolds! When applied and buffed (similar to shoe polish) it provides a very natural medium gray finish. No clue as to whether or not this finish appearance is accurate!