I believe there were many cameras made with chrome on brass. The XE-7 was chrome on brass, and shared many parts with the Leica R-3. IIRC, all of Canon AE-1 production was polycarbonate on the top, part of what made it one of the most feature-rich cameras at a great price, and a runaway best seller. My father-in-law was rough on his Minolta X-700, which was black over polycarbonate, but there is also a shiny brass-colored layer under the black finish and on top of the white polycarbonate top casting. Bottom plates on many of the cameras with polycarbonate tops may be metal to keep them thin and because they seat battery compartments and tripod sockets, so any finish rubbed off there may appear to be a brass color.

Lee