State and Territorial Quarter Photo Gallery
Some of the Wyoming state quarters have a rare flaw called a doubled die. The mistake is caused when the die that stamps the quarter design is tilted and wobbles during the stamping process. The incident causes a second impression to be made at the center of the coin. The Wyoming quarter's flaw can be found around the bucking horse's saddlehorn -- where there's a tip of a 'ghost' saddlehorn.
The error is difficult to see without magnification and therefore might be too small to create much of a premium for it. However, an error in the Minnesota state quarter has sold for over $100, and at one time flawed Wisconsin state quarters sold for over $1000. Only time can tell how much this error might eventually be worth to collectors.
Read more about the Wyoming state quarter error at: Caspar Star-Tribune