Mint error coins can occur in many different ways, and come in all shapes, sizes, and with countless combinations and variations. Mint's are factories, and like all factories, the machinery breaks, people make mistakes, and all of it can result in improperly minted coins. Although there are many ways in which a coin can have an "error", the errors all have definitions (although, new mint error types are discovered form time to time, particularly as the Mint's equipment changes!)
Below, you will see a partial list of some of the mint error types commonly encountered. Of course, the list is not exhaustive, but it includes many different types. We will continue to add to this list over time, so check back often!
mint errors examples
Clipped Planchet: Curved Clip
A curved clip occurs when the sheet of planchet strip is not advanced forwards far enough after having blanks punched out, causing the blanking dies to overlap the previously punched out holes. This results in coins with curved areas of metal missing called a curved clip.
Clipped Planchet: Disc Clip
This clip is defined as being a clip so small, it can only be seen on the rim or in the "shift" of metal on the edge, but which does not effect the coin's diameter in any way. So for example, you might see a small dimple of metal missing on the rim, but this type of mint error coins would still be perfectly "round." On a clad coin , you will see a visible "shift" in the layers of metal on the edge where the disc clip is, but the coin will still be completely round.
Clipped Planchet: Straight Clip
A straight clip occurs when the blanking dies punch planchets out of the planchet strip in such a way that they overlap one of the edges of the planchet strip. The punched out planchet will have a straight edged clip, call a straight clip.
Clipped Planchet: Outside Corner Clip
If the blanking dies overlap one of the corners of the planchet strip, the result will be an outside corner clip. The coin will have a right angled clip. A very rare error type.
Clipped Planchet: Elliptical Clip
An elliptical clip is a coin which is struck on a oval or elliptically clipped planchet. The error is a close relation to the incomplete clip, but is different in that when it punches the previously partially punched planchets, it punches them out all the way resulting in an overlap that produces an elliptically shapped planchet.
Clipped Planchet: Incomplete Clip
This error occurs when the blanking press does not punch all the way through the planchet strip, and then retracts. Then the planchet strip is not advanced forward all the way, resulting in the blanking press punching out planchets which overlapped the previously only partially punched out planchets, leaving an arching line across both sides of the coin.
Clipped Planchet: Ragged Clip
A ragged clip is a coin with a rough, ragged clip area. The shape comes from the end of a coil of planchet strip which had not had it's rough, ragged end cut off, but instead was sent straight into the blank press. The result was a planchet which has a ragged clip.
Off-Metal
An off-metal is a coin struck on a planchet other than what it was intended to be struck on, but also is a planchet which is a different metal than what the coin is normally struck on.
The above coin is a Jefferson nickel struck on a Lincoln cent planchet. It is copper as well, which is different from a nickel's normal metal.
Off-Center
An off-center is a coin which has its design struck off of the planchet. In order to quality as an off-center, there must be design missing on at least one side of the coin, and it also must be struck out of collar (no reeding on the edge except perhaps minor traces.) Diagnostics include
The above coin is an off-center buffalo nickel.
Wrong Planchet
A coin which is struck on any planchet other than what it was intended to be struck on, but being of the same metal as it would normally be struck on (if the normal planchet is nickel, and the coin is struck on a copper plachet it would be an off-metal. If it was struck on a nickel planchet for another series of coin, it would be a wrong planchet error.)
The coin shown is a Washington quarter on a nickel planchet. The coin is nickel, like a normal quarter, but the planchet is actually a Jefferson nickel planchet.