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Error Coins: Doubled Dies vs. Machine Doubling

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Hello Ladies and Gents !

I put an educational series video on Youtube that shows the difference between a normal coin, a coin with machine doubling (strike doubling or mechanical damage) and a doubled die.

The big thing to take away from this video is pretty simple. Let me break down the differences;

Doubled Die (aka Hub Doubling)

  • Doubled Die (aka Hub Doubling) Prior to 1996, the Master die was placed in a high tonnage press
  • A blank working die was warmed up to make the transfer of the design easier.
  • The blank working die was placed below the master die.
  • The dies were pressed together with about 20 tons of pressure.
  • The mint workers did not know if the design features transferred correctly. So they would remove the die and inspect it.
  • If the working die did not have a satisfactory impression from the master die, the die was warmed up and placed back under the master die for another impression (stirkes).
  • When the workers placed the working die for a second and potentially other additional impressions, if the die was not correctly lined up it may cause a second impression to be visible.
  • These additional impressions if they were slightly rotated or off on any axis, it caused the additional impressions to be visible and thus called a "doubled die".
  • Once the die impressions were acceptable, the die was inspected.
  • The newly created die (with multiple impressions) was added to a coin press.
  • This working die with the multiple impressions begins to make coins and will transfer the multiple impressions from the die to the struck planchet (coin blank).
  • These coins are typically business strikes and are released in the community where coin collectors find them and report them to the news and coin collecting societies.


How to recognize a doubled die

  • Doubled dies can be visible on the Obverse or Reverse of the coin, or both.
  • A Doubled die on the obverse (front of the coin) is called a Double Die Obverse (DDO) .
  • A Doubled die on the reverse ( back of the coin) is called a Double Die Reverse (DDR).
  • Doubled dies may be subtle or severe.
  • Doubled dies usually show the doubling at the same height or very close to the same height of the original impression.
  • The features on the coin that are affected by the doubled die may be thicker than normal.
  • The doubled die may exhibit a thin "cookie cutter" style line that indicates where the letters, numbers or features overlap.
  • Doubled dies may exhibit "notching" or an area near the end of a number, letter or device that shows where the doubling ends.
  • Doubled dies typically do not exhibit any sort of damage in the area of doubling. Any damage seen could have been done after the coin left the mint.

Strike doubling, Machine doubling, machine damage, Machine doubling (worthless doubling) indicators

  • Affected areas with mechanical doubling (worthless doubling) typically makes letters look thinner.
  • Mechanical doubling often appears shelf like, with one area lower than the other.
  • Mechanical doubling is only one coin impression with parts of the letters, numbers and devices removed from damage.
  • Mechanical doubling may exhibit damage going in one general direction ( example from south west to north east) on the coin.
  • Mechanical doubling may exhibit sheering lines in the affected area.
  • Mechanical doubling is often caused when a coin is struck, the die does not clear the coin completely and the die collides with the coin and sheers off some of the letters, numbers or devices.
  • Mechanical doubling does not make the affected areas of the coin look thicker, it actually makes the letters thinner.
  • Mechanical doubling does not show the classic notching nor does it exhibit that "cookie cutter" line that separates the impressions. 
  • Mechanical doubling again, may look shelf like, one area higher than the other - a classic sign of machine doubling ( worthless doubling).

Link to the Video:

Educational Series: What is Mechanical doubling? How to identify Mechanical Doubling.




Staff at ErrorCoinCollector.org

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Error Coin Collector Community - https://errorcoincollector.org

Error Coin Collector Online Store - coming soon at https://errorcoincollector.com

Blog - https://minterrors.org

US Coins https://carsoncitydollars.com

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