View attachment 977849 View attachment 977850 View attachment 977850 Any suggestions on what this damage might be? It has a bubble on each side of the coin. Not sure how it happened.
I can't pull up the attachments. Use the upload a file button and post both sides in full scale. Welcome to CT.
Heat damage after it left the Mint. The black spots look like scorching from the heat source. What was used to do this is anybody's uneducated guess.
When the metal layers a bonded together there can be small gas pockets trapped between the layers. If the coin is subjected to high heat the pressure in these gas pockets increases. Once the temperature gets high enough the metal of the clad layers reaches a "plastic" state, not hot enough to be a liquid, not cool enough to be a rigid solid. At this point the gas in the trapped pockets is able to expand stretching the metal of the clad layer and creating bubbles. Once the metal cools you get the hard raised bubbles like the ones you see on your coin. Sometimes the bubble is large and as the temperature drops the bubble will try to collapse, but since it has been stretched it can not return to its original position. On those you will see large deformed areas with the center collapsed.
