Material: Black pound. The oxidation of pure silver devalued the black pound. This blackening will fade over time, but if you're interested (it's a very simple process), we'd love to help you teach you how to re oxidize your work. Also, note that black pounds look darker in photos than in people.
Doctor: dirty brass. This color is achieved by burning metals to release impurities and self coloring purposes. This is produced internally, and no chemicals are added to the surface.