I pulled a hinge off an AD which had never been removed before, and there was what looked like plumber's putty under it which is what GM used to keep rain out of the cab. Once the putty was cleaned off I could see a shiny, metallic silver finish. I have used Rustoleum self-etching primer under Rustoleum metallic silver paint which is a very close duplication of the original finish, which I believe was cadmium plating.
