FWIW, I lightly polished this 1937 Silvertone console radio bezel and then sealed it with Dupli-Color Truck and Van Clearcoat Lacquer. It didn't discolor and it's been several years now with no changes. It's more copper than brass, was bright green when I found it. I didn't polish it clean, tried to leave some of the character. Came out well.
Don't know if Duplicolor paint has MEK in it, will have to check...
Bob, PM received, the knob will go out Tuesday.