First step; is the material magnetic? If so it probably is plated
steel. Usually the plating also has a lacquer coating over the brass
plating to prevent tarnishing. Where you are seeing the "copper"
colour showing through is probably caused by the lacquer being worn
and that area, and the brass plating tarnishing. If it is not
magnetic, then it probably is solid brass, but again would more than
likely have a lacquer finish over.
Richard Dubiel DUBIEL DESIGN STUDIO @Dubiel_Design_Studio Tel
905.566.0950 Fax 905.290.9398