Well, here are a couple of quickly made shots of the underside of a Nikon FA top plate and one image of a scuffed top-right-front corner of the FA top plate showing the gray plastic, some of the bronze paint and, of course, the black painted surface.
Originally Posted by Snapshot
So it looks (and feels) like the whole piece is plastic with a layer of bronze paint and then black paint over that. It also looks like there is some green paint in the area of the shutter button/film counter/film advance lever/mode selector/shutter speed control (underside of top plate). Not sure what that's for.
Anyway,...here you go.