In numismatics there are many details to look for and many different types of coins and currency to collect. One area that is often over looked by the new collector is mint-made errors. Error coins and currency are those lovable mistakes that are usually caught by the mint before they ever get a chance to reach circulation. But, no one is perfect. Sometimes these errors make it out of the mint, and you are certainly a lucky duck if you find one in your change. Here are a few different kinds of error coins to look for.
Planchet Preparation Errors
To prepare lancets on which to strike coins, a mint first purchases strips of metal of the correct composition of the coin to be produced. These strips are fed through a blanking machine that cuts them into the metal disks on which the coins are struck, which are known as blanks or lancets. The shape of the coin, whether it be circular, rectangular, or any other shape, is determined by the manner in which the blanking machine shapes the lancets. At this stage, the blanks are type 1 blanks. Next, these type 1 blanks go into an upending mill, which gives the blanks an upended rim, which is where the rim becomes slightly raised and rounds off to the center of the lancet. Lancets with upended rims are called type 2 lancets.
Occasionally a misdeed can occur where the strip of metal is not fed through the blanking machine far enough. When this happens, the punches strike an area of the strip which overlaps the hole left by the previous strike. The result is a blank with a piece missing, which is called a clipped lancet. A clipped lancet may be straight, curved, ragged, or elliptical.
Die Crack, Break, Chip or Clash
When the coin is stamped with the die, there are a multitude of problems that could occur. A die crack will result in a coin that has a raised, jagged line on its surface. A die break or chip will show a raised unstuck area on the coin. And a die clashwhich occurs when the obverse and reverse dies strike each other because a lancet is not between them. Due to the tremendous pressure used, the parts of the image of one die may be impressed on the other. When lancets are then fed between them the resulting coins receive the distorted image. A well-known example is the "Bugs Bunny" Franklin Half Dollar of 1955, where part of the eagle's wing from the reverse gives Franklin the image of protruding teeth.
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Overate/Repented Date or Mint Mark
This can happen either by accident or intentionally. In the past, to save money the mint would use a die until it broke. When the years would change, the dies were altered to show the new year. This resulted in a faint previous date to show on the coin. As for mintmarks, a die technicians punch the coins with a mint mark. If the first punch is faint the technician would stamp the coin again.
If a coin fails to be properly ejected from the striking chamber after being stuck and the dies come down again to strike the coin again, a double strike occurs. Double strikes can occur with the second strike off center or on-center. In the same way triple and multiply struck coins occur.
A clad coin with one of the clad layers missing either before the coin is struck or which is loose and falls away after the strike. The side of the coin with the clad layer missing will be copper colored showing the exposed copper core of the coin. The other side of the coin is normal.
If the impurity is severe enough, it can case the lancet to split into two halves obi. and rev. If the lancet splits before the strike, the resulting coin will be thin and have detail on both sides but often intermingled with rough striations from the impurities. If the lancet splits after the strike, one side will have full detail and the other side will be blank and striated. In either case the coin will be thin.
Dirt and impurities in the metal of the lancet can manifest themselves as cracks and peels on the struck coin.
Fold along the corner of a note which after the cutting process results in an excess flag of paper, sometimes roughly resembling a butterfly's wing.
Error note featuring mismatched front and back values (eg. $10 face design with a $5 back design)
When currency is printed, it is printed in a series of passes. Sometimes bills are released missing first, second or third printing. Which results in missing serial numbers, seals or detail.
Modern note with a star symbol in the serial number distinguishing it as a replacement for a note that was removed because it contained a flaw that was caught. Please note, early U.S. currency, generally before Series 1899, often contain stars and other symbols as part of the normal serial number and do not represent replacement issues.
There are many more errors to look for but this is enough to get you started. Once you get bitten by the error coin/currency bug you will start looking through your collection to see if you have any errors. Once considered mistakes, these errors make the coins just a bit more special.