Nope not an error. It's a stain from some sticky residue that got on the coin. It could of been in a dirty car cup holder. It's Post Strike Damage (it happened after it left the U.S. Mint).
Disclaimer: While a tremendous amount of effort goes into ensuring the accuracy of the information contained in this site, Coin Community assumes no liability for errors. Copyright 2005 - 2026 Coin Community Family- all rights reserved worldwide. Use of any images or content on this website without prior written permission of Coin Community or the original lender is strictly prohibited. Contact Us | Advertise Here | Privacy Policy / Terms of Use