I'm a designer and am doing a project which will involve creating an artwork with thousands of coins. This questions in two parts: 1. Which coins would be the most cost effective to buy. I need a silver looking coin and a brass looking coin. 2. Where could I purchase these coins. (I'm watching bun pennies on eBay but feel there has got to be a simpler way to purchase) 3. Naturally budget is an issue as with all projects of this type. I really don't want to have to use currency in current circulation. Any thoughts on this matter greatly appreciated.