First of all do NOT clean it you will completely destroy its value! Its value depends on its condition, the variation of the coin (there were several different styles for this coin) and what it is made of. In an absolutely worn down condition it is worth about $7500. If it is in good shape they can go from $20,000 to $400,000 depending on its composition and style. If yours is in perfect condition (unlikely) it can go anywhere from $62,000 to $700,000 depending on it composition and style. I suggest that you immediately wrap it in an extremely soft fabric and bring it to a PCGS authorized dealer coin dealer (search the PCGS website). If there are none in your area contact PCGS about how to become a member so that you can have it submitted and graded. (This is why going to an authorized dealer is best.) If you don't get it graded you will be lucky to even get a fraction of its actual value whenever you decide to sell it.
