Selling old dental crowns?

When my dentist gave me the crown that went kerfluey (highly technical, I know) last time, she suggested I explore selling it. I had no idea people bought old growns for the gold in them. A Google search gave me some interesting information, I'm going to have to look further. I know it's not much money, but I'll take pennies over a broken crown. Subsidize the new one :)