Golden artist acrylic paint, carbon black, flat if you can find it, and a small brush, should do the trick nicely. Just be sure to clean the metal with some alcohol, air dry and when the paint is dry, heat-set it with a hair dryer set on 'high' heat. Best you remove the piece from the body because of the heat-set.
"An armed society is a polite society. Manners are good when one may have to back up his acts with his life." Robert Heinlein
"The power to tax involves the power to destroy;...the power to destroy may defeat and render useless the power to create...." Also Robert Heinlein