http://www.fleamarketgardening.org/2013/01/15/aging-pots-and-metal-in-the-garden/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+FleaMarketGardening+(Flea+Market+Gardening) (look for the penny ball)
also, I'm not sure how to credit her in this, but if you are looking for more ways to antique or age your metal, then follow 'Laura Z', she has a great board on Pinterest!