2015 Saratoga Quarter

to the CCF!

It looks like this coin was damaged in a fire. The clad layer has separated and bubbled up from the copper core. The devices have soot and discoloration around the edges which is often seen with fire damaged coins. Not an error or collectable this time, just Post Mint Damage. PMD

and I agree,fire damaged.
John1

to the Community. Heat damaged.

head damaged post mint. no mint error, sorry.

to the CCF!

Welcome to CCF!

to the CCF and

It doesn't really matter if it is heat damage, corrosion or anything else.
The fact that it could not happen during the striking of the coin
automatically makes it PMD. Damage is damage.

The coin is clad, which means there is a thin core of copper sandwiched between two even thinner layers of a copper nickel alloy.

Inevitably, during the cladding process, a little bit of gas is trapped in between they layers.

When heat is applied, the trapped gas expands and has to go somewhere, so the bubbles you see are produced. Because the gas expands at a lower temperature than the the metals, you often won't see heat damage to the metals.

However, because the outer clad layer is so much thinner than the center core, it frequently softens in the heat, allowing the expanding gas bubbles to cause the distortions you are seeing.

As to it being localized, that can depend on the heat source. A soldering iron or a wood burning tool or even a small hot coal in a camp fire can cause a localized temperature increase that produces these bubbles.

Put a blow torch to a solid, non clad coin, such as a nickel or a pre 1982 cent and you'll see an entirely different effect. Instead of bubbles forming, because there's no trapped gas, you'll see waves on the coin's surface, caused by the melting metal interacting with the heat source.

Different coin construction results in different responses to heat application.