Many people have emailed about possible error coins that they have found in circulation. Discovering an error coin can be a rewarding experience and it may often result in a nice profit. Error coins recognized by the American Numismatic Association are those that are legitimate mint processing errors and they come in several forms. The best place to obtain information about coin errors is to puchase a coin guide.

Modern Day Minting Process
Modern day minting starts with a strip of metal that has been specifically produced for the manufacturing of coins. Each sheet is fabricated to the tolerances provided by the mint. The process begins with taking a strip of metal and then blanking out coins in a press. The blank coins are known as planchets. One mint error is when the blank planchet escapes the coining process and ends up in a mint bag of coins.

A defective planchet is caused from impurities in the metal itself that is used to make a coin. The surface of the coin will appear ragged and often times the inner metal may show such as the clad in a dime or a quarter. A lamination error occurs when the surface of the coin looks like it is peeling off. A lamination error is caused by impurities in the metal used in the blanking process or by some debris that was in the stamping dies. A split or broken planchet occurs when there is a line on the coin which is actually a crack. Anotherl mint processing error is caused from the blanking process where a piece of the blank is missing. When a piece of the blank is missing the coin is called a clipped planchet. Clipped planchets come in several forms; curved clips, ragged clips, and a host of others; all having missing metal.

Minting Errors
If a planchet is too think it will cause some of the obverse or reverse detail to be missing or lightly stamped.  In addition to think planchet errors there are errors where a coin is minted on the incorrect planchet. These errors occur when stock from one coin batch is mixed with another. There have been some issues with the state quarters being minted on dollar stock. These coins are rare in circulation since most of them are caught by banks and coin dealers before they get out into circulation.

Die errors are another kind of error that in recent times has been slowed by the upgrading of the mint dies and the re-polishing of the dies on a frequent basis. Some mint errors are caused by the coin being stamped out of the collar. The coins that are minted out of the collar are larger than a normal coin because the metal expands with out a device holding the coins circumference. Collectors call these coins broad struck. In addition coins could actually be double struck in the press.

Double dies are another type of mint error. These types of errors are extremely rare and as evidence of this is the low frequency of coins that are notably double die errors. The most famous double die error remains the 1955 Lincoln cent.

Other types of minting errors are in the form of die cracks which leave a rough line across the path of the die break on the surface of the coins. The minting of the coin will leave a ridge of metal across the surface of the coin. There are also die breaks that cause indentations in the coin.

Double mint marks are caused by re-punching a die inaccurately causing a double mint mark or a dual mint mark on a coin. These errors are widely known as RPM's.

An OMM or over mint mark is when a die has been uncleanly changed from one mint mark to another. Coins minted in with these dies appear to have one mint mark stamped over another such as S over D.

Another type of error that is worth noting is the rotated coin error. These coins are partially rotated from the natural rotating of 180 degrees. This type of error should not happen with modern day coinage since the mint stamps both the obverse and reverse at the same time.

I have not named all of the possible die errors, but I have named the most popular.

So what are not considered real mint errors?
Color of a coin
One question that is often asked is about the color of a coin and it is my favorite question. There are no published notifications of coins being produced with any different colors than that of the present day copper colored or silver coin. There are no "yellow" or "silver" Lincoln cents. There were never any steel cents made before or after 1943. Most likely if you find a coin that is colored, it is the result of a practical joke caused from someone plating or spray painting a coin. A plated coin is usually greasy to the touch and you should be able to scrap off the layer of plating.

Date is missing some numbers
There are numerous coins in circulation that have partial dates of very lightly stamped dates. These are not considered minting errors, however they are the result of worn dies. The dates of some 2000 Roosevelt dimes can be located with the last zero lightly, partially or completely missing. I have several of these coins I keep because they look like the year 200 and are a novelty. These coins are not worth more than face value. Natural wear may obliterate some of the numbers of a date. Most mint errors are simply not going to make into circulation.

Mint marked coins with an S on coins in the 1990's and 2000's
There are no coins make for circulation with the S mint mark. These are all from proof sets that someone has spent. I have personally found dimes, nickels and quarters with S mint marks on them from pocket change. Why people break up proof sets is beyond my understanding since you can get a lot more keeping the set together.

So where do most mint errors come from?
Rolls and bags of coins are shipped from the US Mint to the Federal Reserve Banks. The Federal reserve banks roll the coins and then ship them to banks for distribution to the general public. People then find the error coins in uncirculated condition from the rolls. If you really want to find an error coin, go to the bank and ask for new dated rolls of coins. Smaller banks obtain rolled coin from armored car services. These companies obtain bags of new and old coins, roll them, then distribute them to banks.