Quote Originally Posted by Sciuropterus
Go to a stained-glass supply place and get a bottle of Novacan lead patina (or similar brand)- it's cheap.
It will turn pewter black. Works on some other metals also. If the pin is chrome, you might have to scuff it with an abrasive pad first.
If you don't have any local stained glass stores, just let me know. I always have black patina around since I make stained glass for a living.