Not sure why period correct matters for the OP, based on his requests for something functional. The Pletscher racks lack lateral stiffness from my recollections.

How about the smaller but plenty stiff and strong Tubus Fly, made from steel tubing (like most Tubus racks), available in either black powder coat or stainless (Matt silver) that attaches to the brake bolt? They are excellent with panniers, but the top is not wide enough for a rack bag. Instead, we use largish seat-post mounted bags that end up resting on that top surface.

Tubus Fly Evo Rear Rack ? TheTouringStore.com

And to answer the original question, I think a silver rack would look great, especially with the chrome socks of the frame.