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There is a marked difference between die deterioration and machine doubling.
Die deterioration doubling is a natural effect, caused by the metal moving over the die face and eroding it. As the die ages, metal flow will start to hollow out places on the die, normal next to a design element and in a direction away from the center. This hollowing out of the die face leaves raised areas on the coin which appear to be a duplicate of the design element, but in reality, they are not.
Machine doubling is a function of a loose or chattering die. What happens here is that the coin, after the initial strike, will bounce up and hit the retreating die again. The affect design elements are not actually doubled, but a portion of them become flattened due to this erroneous strike, giving it the appearance of extra thickness and doubling.
BJ Neff
Die deterioration doubling is a natural effect, caused by the metal moving over the die face and eroding it. As the die ages, metal flow will start to hollow out places on the die, normal next to a design element and in a direction away from the center. This hollowing out of the die face leaves raised areas on the coin which appear to be a duplicate of the design element, but in reality, they are not.
Machine doubling is a function of a loose or chattering die. What happens here is that the coin, after the initial strike, will bounce up and hit the retreating die again. The affect design elements are not actually doubled, but a portion of them become flattened due to this erroneous strike, giving it the appearance of extra thickness and doubling.
BJ Neff
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