A capped die is caused when a struck coin sticks to the upper hammer die. Once the coin is stuck to the die face, the reverse of the struck coin becomes the new die face. When the next blank is fed into the collar and the strike occurs, the reverse design of the
adhered struck coin impresses itself into the new blank. This struck coin is a brockage strike. The coin adhered to the upper die is known as a die cap. This process repeats itself as more coins are struck by the cap. The greater the number of strikes, the higher the cap metal will be pushed around the upper die shaft. Eventually, the cap brakes away from the die in the shape of a thimble.
Images courtesy of Byers
Two Piece Obverse Capped Dime Die
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