U.S. Coin Library

Classification of Mint Errors

Information

This section provides a list of all major errors and explains how they occur. Classification of mint errors is divided into two categories. Planchet errors affect the piece before it is struck with the dies. Coinage press errors are associated with the actual striking of the planchet.

Planchet Errors

• Blank planchets - This error occurs when blanks intended for coinage are punched from the metal sheets but escape from the mint without ever having been struck with dies. There are two kinds of blank planchets. Early-stage Type 1 blank planchets have a raw, unmilled rim. Type 2 blank planchets are later-stage pieces that exhibit an upset or milled rim. The Type 1 planchets are generally considered to be more valuable.

• Clipped planchets - Clipped planchets or "clips" result when the steel rods used to punch out planchets from the metal strips overlap a portion of the strip that has already been punched. Several different kinds of clips exist. Curved clips are the most frequently encountered. Straight clips are made when the blanking press punches out planchets along the smooth edge of a metal sheet. When the blanking press overlaps the irregularly cut end of a metal strip, it results in a ragged clip. Elliptical clips, the rarest kind, are formed when an incompletely-punched sheet of metal is fed into the blanking press a second time, producing one or more incompletely-punched planchets. These planchets then break apart along the seam formed by the incomplete punch and the football-shaped, or elliptical, portion is then struck by the dies.

• Incomplete punches or Incomplete clips - Similar to elliptical clips, incomplete punches occur when an incompletely-punched sheet of metal is fed into the blanking press a second time, producing one or more incompletely-punched planchets. When these planchets are struck by the dies, the resulting coins will exhibit a curved line or seam through the center and may appear to be slightly bent.

• Lamination - Lamination flaws occur when dirt or other foreign material becomes trapped in the metal sheets as they are rolled out to the proper thickness. Coins struck on planchets made from these contaminated sheets will have noticeable flaws, such as a portion of metal peeling off the coin's surface. In a related situation, copper clad or silver clad coins that are missing a complete clad surface on one or both sides are termed as missing clad layer(s) and are much more valuable.

• Unplated planchets - This category refers specifically to cent planchets made from 1982 to the present that simply bypass the copper-plating process. Specimens that are struck with the cent dies are worth far more than the blanks that have not been struck.

• Wrong planchets or metals - These errors result when a coin is struck on a blank intended for another denomination (e.g.: cents on dime planchets, nickels on cent planchets, etc.) Occasionally, a coin is struck on a fully-struck coin of another denomination. These errors are more scarce and command much higher prices. Some examples are: nickels struck on cents ("six-cent pieces"), and dimes struck on cents ("eleven-cent pieces"). In the past the United States has been known to produce coins for other countries. In some cases, this has produced U.S. denomination coins that are struck on foreign planchets of odd weight, color, and size.

• Wrong stock - Sometimes planchets are punched out of sheets intended for another denomination (for example, quarter planchets punched out of dime stock). These coins will have the correct diameter, but improper thickness and weight.

Coinage Press Errors

• Broadstrikes - Error coins of this category are formed when the collar is not in place to contain the metal of the planchet as it spreads during the strike. All error coins of this category will have a plain edge and will usually be larger in diameter than normal.

• Brockage - These errors are caused when a struck coin remains on either die after striking, and impresses its image into the next planchet as it is struck. This creates a negative or mirror image on the latter coin. "Early stage" brockage pieces, with a sharper mirrored image, are valued higher.

• Caps - This spectacular error occurs when a struck planchet becomes stuck to one of the dies. After repeated striking, the coin's metal stretches around the sides of the die creating a shape similar to a bottle cap. Caps are extremely rare, especially on higher denominations with lower mintage.

• Chain strikes - Chain strikes are formed when two coins fall into the collar side by side. When they are struck, each receives part of the design of the dies. As the planchets' metal spreads during the strike, they will press together. The result is similar to two puzzle pieces. When the two coins are placed next to each other, they will form a full coin design, with each part of the design on each coin.

• Counterbrockage - Counterbrockage errors occur when a brockage coin remains on either die and impresses its negative image into the next planchet as it is struck (see Brockage). These pieces will have an indistinct and somewhat larger raised image on one side.

• Defective die(s) - Coins struck with defective dies will show raised metal from large die cracks or rim breaks. Cuds or areas that have not been struck are formed when an entire piece of one die breaks away. Prices vary depending on the size and nature of the die defect.

• Die trials and Die set-up strikes - This type of error coin results when the coinage press strikes the planchet with too little pressure. Characteristics of these pieces will be extremely flat and poorly formed designs on both obverse and reverse and a smooth edge on denominations larger than the nickel. The smooth edge results from the planchet's inability to spread to the reeding of the collar due to the weakness of the strike.

• Indented strikes - These error coins are made when a planchet is partially overlapped by another planchet during the strike. The latter planchet is "struck into" the former, creating an indented area on that coin in which no design details are visible. Indented strikes, like most other errors, can happen in any denomination. Coins that are completely overlapped by a planchet of another denomination smaller in size command much higher prices.

• Multiple strikes - Multiple strike errors happen when a struck coin fails to be ejected from the coinage press and is struck again off center. Value of these coins increases with the number of multiple strikes they possess.

• Off center strikes - This error occurs when the coin is improperly fed into the coinage press and is not centered when struck with the dies.

• Partial collars - Similar to broadstrikes, partial collar errors are formed when the collar is only partly in place to contain the metal of the planchet during the strike. The rim of such coins will exhibit two distinct diameters. That of correct diameter for the denomination, and one of larger diameter as that of a broadstruck coin.

• Struck-through errors - Coins of this category will demonstrate a depressed area due to foreign material becoming trapped between the dies and the planchet during the strike. The foreign material may include almost any substance, including cloth, grease, string, wire or scrap metal.

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