clad coins heated up or have been a fire tend do this .... your quarter looks discolored which is probably what happened
A filled die would be a "struck through" error where part of the detail of the design is missing. What you have is PMD...a coin damaged outside the mint. Worth face value. Keep up the hunt!
OK thanks again people. It is amazing that only one side was affected. Other side is normal. USUALLY heat affects BOTH sides. Back to science class I guess.
I have some halves that are exactly the same. Fine on one side, bulging on the other. All were in a fire. Apparently coins have small air bubbles in them and they tend to expand toward the thinner side only when the coin is hot.
Heat does affect both sides but the effects of an expanding air bubble in the coin can differ from one side to the other. Correct. Suppose a trapped air bubble happens to be closer to one side of a coin. When the coin is heated the pressure in the trapped air bubble will increase. If the coin is heated to a high enough temperature the metal in the coin will become plastic which will allow the air bubble to expand in size (and decrease the pressure inside the air bubble). The bubble will expand in the direction of least resistance which is usually where the metal is thinnest between the air bubble and the surface of the coin.