Modern minting errors

August 18, 2014 By ekr


By William Cather

In the modern minting process due to the mechanical process of minting the coins there are countless errors that can occur. There are four main ways that these errors categorize in. These ways are  striking errors, die errors, planchet errors, and die varieties. Varieties and Errors are both similar and different in comparison. A error is a occurrence in the coin that does not repeat exactly and a variety is a occurrence that does repeat exactly.

Striking errors are errors that are the mot visible minting errors. Classification of striking errors are struck-on-abnormal-planchet, die-adjustment-strike, struck-through-abnormal-object, multiple-strike, collar-striking, multiple-planchet-strike, mated-and-matched-pair, misaligned-and-rotated-strike, lettered-and-design-edge-strike, defective-strikes-and-mismatched-die, and multiple errors all fall under the category of striking errors. Each of these errors can occur from both human and mechanical error inside of the minting facility itself. Striking errors are also the most sought after type of error for error coin collectors since the minting facility can spot these types of errors so easily.

Coins struck on abnormal planchets are very obvious and easily detectable to the minting facility. This type of striking error is caused by mechanical error in the minting process. Both foreign objects and incorrect planchets have been struck incorrectly. The foreign objects consist of things like nails, washers, and occasionally knockout plugs. Incorrect planchets consist of half dollars struck on dime stock, dollars struck on quarter stock, etc. 

Die-adjustment strikes are strikes such as a weak, strong, edge, or a edge die-adjustment strike.

These strikes are caused from the pressure for the coin to be struck improperly calculated. A weak strike is caused when the pressure is set to low and a strong strike  is when the pressure is set to high. A edge strike is quite different though. A edge strike is when a planchet is standing on edge and the edge of the planchet was stuck in stead of the obverse and reverse of the coin. A edge die-adjustment strike is when either the letter on the edge of the coin is either weak or completely missing due to improper pressure on the edge striking.

A struck-through-abnormal-object errors are quite unique too. These types of striking errors are both mechanical and human caused. The types of struck-through-abnormal-object errors are vast. These types of abnormal objects can be cloth, thread or string, rim burr, feeder fingers, unstruck planchets,wrong-metal fragments, debris such as grease and dirt, wire, split-off reeding, miscellaneous objects, dropped filling, and struck-through progression. These coins all have clear and evident errors when examined.  All of these types have what you would think is wrong with them clearly except for struck-through progression. Struck-through progression is when there are two or possibly more coins that evidently show that they were struck through the exact same debris.

Multiple-strike errors is when a coin gets struck twice or more by the dies. This occurs mainly when the coin is not ejected out of the coining chamber correctly. The coin is always struck the same amount of times on both sides with one exception. The exception is when on side has a loose die and causes the coin to get struck with a doubling effect even though it is technically not being struck twice by the die.

A collar-strike error occurs when the coin is improperly struck by the collar machine which is the third part in the minting process for coins. The collar-strike error can occur as a broadstrike, flanged partial-collar strike, off-center strike, wire-edge strike, or a high-collar strike. The way and reason these occur normally is when debris or part of a planchet jams the collar machine; causing the coin to be struck partially or fully out of the collar of the coin. Most of these errors are quite easy to spot but a few such as flanged partial-collar striking, tilted partial-collar strike, and the reverse- flanged partial-collar strike are not as easy to spot.

The multiple-planchet strike error is an interesting type of error. This normally only happens to two planchets but has also happened to a three or more planchets as well. This occurrence can happen in almost any denomination of coinage. This type of strike can happen when the coin has either a matched or mated pair after the striking. Mated pairs are pairs that were struck and fit together perfectly. Matched pairs are pairs that are from similar strikes but do not fit together perfectly. 

Another fairly well known type of currency error during the modern minting process is the misaligned and rotated strike error. The way that this occurs is when the planchet is being struck the positioning of the planchet is off, tilted or rotated any amount of degrees. The sub-categories that are within this type of error include offset die-misalignment, vertical die-misalignment, and the rotated-die strike. Each of these sub-categories are just the different variations of the main category of misaligned and rotated strike errors.

The final type of error I will be talking about is the lettered and design edge strike error. This error pertains to when a coin with either a lettered or designed edge has an error occurring with it. This can happen when the edge motto or design overlaps itself. It can also occur when the coin has the wrong edge motto or design or even if it is completely missing from the coin itself. It can receive a jammed edge die from having a segmented die that was jammed during the striking process that it  was currently going through at the time. The final way a coin can gain a edge striking error is if it has a misplaced edge-die segment when its edge was being struck.

These are most of the broad spectrum of the coin error world for numismatics. The types of errors also show the vast array of the mishaps that can take place throughout the minting process. Besides errors in the modern minting process a numerous amount of assorted varieties occur too. This type of numismatic collecting is fairly popular and is very interesting to collect and learn about. 

Bibliographic List of Sources: 

  • The Modern Minting Process & U.S. Minting Errors & Varieties, By: James Wiles Ph.D.
  • The Official Red Book: A Guide Book of United States Coins, By: R.S. Yeoman

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