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1999 Dime with a bump in the center
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<p>[QUOTE="Conder101, post: 1269185, member: 66"]It is the result of heat. The coin is heated to just a little below the melting point of the metal. At that point the metal is "plastic". Any gas bubbles trapped inside the coin can expand and "blow bubbles". The design of the coin can still be seen on the surface of the bubble. As the coin cools the metal solidifies and holds the shape of the bubble. Since the dies are essentially flat this is the only way you can have the design on the raised bubble. Some people have suggested in the past that the bubble came for the heating of the planchet created during the striking, but that isn't possible because the temperature rise from striking isn't more than 200 degrees at the most (a coin straight out of the die after striking is hot enough to burn you.) and that is WAY below to point at which the metal becomes "plastic".[/QUOTE]</p><p><br /></p>
[QUOTE="Conder101, post: 1269185, member: 66"]It is the result of heat. The coin is heated to just a little below the melting point of the metal. At that point the metal is "plastic". Any gas bubbles trapped inside the coin can expand and "blow bubbles". The design of the coin can still be seen on the surface of the bubble. As the coin cools the metal solidifies and holds the shape of the bubble. Since the dies are essentially flat this is the only way you can have the design on the raised bubble. Some people have suggested in the past that the bubble came for the heating of the planchet created during the striking, but that isn't possible because the temperature rise from striking isn't more than 200 degrees at the most (a coin straight out of the die after striking is hot enough to burn you.) and that is WAY below to point at which the metal becomes "plastic".[/QUOTE]
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1999 Dime with a bump in the center
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