What Is A Toned Coin?

toning is the natural process where molecules on the coin react to gasses in the atmosphere. Every coin tones. Every coin you have ever touched is toned in some way. Nickels, for instance, are yellowish when they are stamped. Their color mellows before you get one in circulation or from a mint set. Cents are brighter, clad's are whiter... I liked it to if you have ever been on a brewery tour. Beer tastes different when it's minutes old... coins are the same way. Over time coins develope toning in a number of ways. Some gets spots or turn hazy yellow. Others turn brown. Some turn green. It's all a matter of the way the metals are constructed on a molecular level and what types of exposure they have. Colorful rainbow coins tend to turn up when coins come into contact with some other chemical - such as certain types of paper, or fabrics. The toning can be attractive and make the coin sell for a premium- or be ugly and cause dealers to dip the coin (to make it white again) before they sell it. I hope this helps explain toned coins.

Thanks for the great explanation and the picture!