I am restoring a 1912 commercial roadster. The windshield that came with the car is the type that folds aft and locks into place when fully raised. I am not sure what manufacturer made it. It is also black, but appears brass underneath the seemingly anodized coating. Beneath the black coating is a reddish colored coating over the brass. What is it? What is the coating? How to restore the proper finish. I suspect it is brass and aged with a resistant patina. What is the best treatment for this condition? Am i about to destroy a finish unknowingly?