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Just as nearly every family has it's "black sheep" (a member who is perceived as disgraceful or undesirable), so, too does virtually every coin series has it's failures. These are known as errors or mis struck coins, and have a following all their own. (Although freshly minted coins are carefully screened at the Mint, some errors manage to escape the process and land in mint-sewn bags, later to be sent to banks.) Both their scarcity and novelty attract new error coin collectors every year.

There are many different errors in processing and striking, but only the major types will be covered here. For the benefit of clarity, you can click on the examples to view enlargements, or place your mouse pointer over the underlined blue headings for a simplified animation on how this error was made.

Under normal circumstances, the striking process involves the introduction of coin "blanks" into the coin press, where they are struck, then ejected after hopefully make a good impression. (Insecure, the whole lot.) This is almost always the case, but, alas, the products of man are not always perfect...


Our first example is a blank planchet, or coin blank. (Blank planchet is easier understood than a blank blank. Besides, you might think I'm cursing.) There are two types: one which has been freshly cut in the blanking press (Type One), and one which has slightly raised rims after going through a softening process (Type Two). They simply slipped by the striking presses (probably couldn't stand the pressure, anyway). These are the most common type of error, with blank pennies trading among dealers for around 10¢ apiece.  

   
The clipped planchet error occurs during the stamping process, where thin sheets of metal are fed into a stamping machine that punches out rows of coin blanks. If the sheet shifts (don't say that too fast) during the process, blanks may have sections missing where previous blanks have been removed (see illustration), creating a curved clip. A straight clip, on the other hand, comes from an incomplete stamping along the edge. This is another relatively common error.  

   
One of the more dramatic errors, the off-center strike happens when a coin blank is mis-fed into the coin press and only part of the planchet is struck. Each error is different, and is categorized by two different measurements: The amount of the coin design that is visible (i.e., 25% off center), and where the off center design is located in reference to a clock. (The coin pictured would be off center at 2:00. I tend to wait until happy hour.) Some collectors make clocks with an appropriate off center coin at each hour on the dial face.  

   
Probably the best known error coin type is the off-center. No two off center strikes are ever identical. The off center error occurs when the blank falls in a random manner so that it is partly off the lower die just prior to striking. Generally, the larger the coin, the more chance there is of the coin cupping, or bending when the die strikes. This creates a more dramatic appearance.

The example is a 1964 Kennedy half dollar which was struck 70% off center and cupped. The strike is exceptional, and indicative of fresh dies. This particular item is rumored to have been in the personal collection of a mint official who was employed with the mint at the time.
 

   
The double strike error can be the result from several situations. As the illustration shows, a double strike can occur from one die. However, the Mint utilizes two to four dies in close proximity to increase production. A multiple strike could also happen when a coin is struck, then bounces from table vibration into the path of another die. At press speed of two strikes per second, this is a possibility, as are other scenarios. This error is the most popular among collectors and the biggest attention-getter.  

   
The eye appeal of the multiple strike error coin has made it one of the most sought after types. The more obvious the encroachment of the second and third strikes on the first strike, the greater the interest. More often than not, though, multiple strikes appear as almost shadows of previous strikes, being very close together due to the high speed machinery. What makes this type even more desirable is the appearance of more than one date, as well as the presence of the reverse image on the strikings (in lieu of uniface strikes, which are more common).

The example at left is a recent Jefferson nickel that clearly has two additional strikes, one 75% off-center, and the other 90% off-center. The strikings are also referred to as DSBS, or Die Struck Both Sides. Distortion of the initial strike is evident from the additional strikings, partcularly on Monticello.
 

   
This error type occurs when dirt or debris lodge between the plate collar and the lower die, inhibiting its movement. If the die is stuck in the up position as shown in the animation, the planchet will spread into a bowl-like object when struck. If the entire design is visible on the error, it is considered a broadstrike. If, however, any part of the design is missing due to the coin not being centered under the die, then it's considered to be an off center error. This mis strike does not share the same level of popularity as other errors, but is still an important error type.  

   
A capped die is simply a coin that for some reason sticks to the upper die during striking, and through multiple strikings thins out and molds around the top or obverse die, forming a cap similar to a bottle cap or thimble. The greater the number of strikes, the higher the cap metal will be pushed around the upper die shaft.

The cap error coin is an extremely spectacular error type which is quite scarce and virtually unavailable in larger denominations due to their smaller mintages.

The present example is the plate coin on page 214 in The Error Coin Encyclopedia. It is a 1970 Denver minted cent that is particularly deep from numerous strikings, and having the reverse design virtually obliterated. Although deep die caps often have damage due to splitting off from the die, this specimen has nearly perfect facing and rims.
 

   
Bonded coins occur when there is a major disruption of the planchet feeder system for the coinage presses. If the struck coin is not ejected properly and another planchet is fed into or near the same collar, part of that struck coin will land on top of the previously unejected strike. The two coins may be crimped and subsequently bonded together. If this process repeats, more will join in the bonding.

Bonded coins rarely escape the mints, except through the shipping of bulk, uncounted but weighed coinage, or with the assistance of an unscrupulous mint employee. Recently, the Secret Service has determined that those bonded sets of more than three coins are subject to confiscation, due to the fact than most are from clandestine release.

The specimen at left is a three-coin bonded set of 1990 Philadelphia minted cents. These items are exceedingly fascinating to view.
 

   
Another very dramatic mint error is a coin struck on a previously struck coin. An example of this type would be a cent struck on a previously struck dime. Here, we will see elements of each design on the struck coin. The wrong planchet error occurs from the use of older "tote bins" which are used to carry the blanks and struck coins from place to place. These are large steel tubs with sloped bottoms which allow the emptying of the bin completely when a slide trap door is opened. Occasionally, a blank or struck coin will remain stuck in the crevices of the bin and escape unnoticed. Later, when that particular bin is used to carry other struck coins, the trapped piece will be dislodged and mixed with the rest of the contents. Thus, double denominations happen.

The coin displayed here is a 1996 dime which was later struck with cent dies. These double denominations tend to be the most common and least expensive of this error type, though they still command $400 to $700, depending on the date and grade.
 

   
Like the mix of a horse and donkey, a mule in coin errors is an unlikely combination of two incompatible entities: a different denomination from mismatched dies on each side. Although they are not uncommon in European and Asian coinages, the appearance of these in the U.S. is very rare, mainly because the different denominations are of differing diameters, so dies are generally incompatible.

Recently, however, several mules have come to light. One which has received quite a bit of press is the Sacagawea dollar planchet and reverse/ Washington quarter obverse. 10 to date have made their appearance in the East and Mideast United States beginning in mid-2000. (Frank Wallis, the finder of the discovery, or first piece, had contacted Studium for information on its origin and authenticity. Pardon my momentary name-dropping.)

Another mule of which only two have been discovered is a Lincoln cent planchet and obverse/Roosevelt dime reverse. One is dated 1995, the other 1999. Due to their extreme rarity, documented prices realized for this type of error have ranged from $25,000 to over $80,000.
 

   
     
     

References: The Error Coin Encyclopedia - Third Edition - Margolis-Weinberg - 2000

 

         
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