This 1978 quarter has 2 lumps in it. I'm curious if this is something that could have occurred from mint or if something happened to it afterwards. The obverse is perfectly fine with no recess or any kind of damage at all so it is either extra metal on coin or some kind of internal bubble?
Internal bubble is on the right track. This coin was heated by an extreme source of heat. The interior copper core melted, expanding and warping the exterior nickel cladding, which has a higher melting temperature than copper. But at that temperature the nickel is in a ductile transition state and can expand to the increased interior pressure from the copper.
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 - 2021 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