Your header says 1977 but the lettering of IGWT is actually of a later issue of the 80's or 90's which then would be a plating bubble issue as E&V stated. Otherwise all it could be on a copper/bronze coin would be a metallic reaction to a caustic chemical in droplet form.
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