Rather than making coins by stamping the design and punching them out of a strip of metal in a single step, most coin designs are pressed into individual circular blanks called planchets. This allows for the edges to be raised in a process called “upsetting” and for edge designs such as reeding and lettering to be added during the production of the coins.

Ribbons of Metal

Planchets are normally stamped from long rolls of metal. These rolls are made to exacting standards of composition and thickness, depending on the coins to be made from them. Other than bullion coins and some collector coins, the rolls come in the form of a composite “sandwich”—copper-plated zinc for cents and nickel-plated copper for dimes, quarters, and half dollars. Nickels are made from an alloy of nickel and copper rather than being cladded.

These rolls of coin metal are fed into blanking punches where disks of the appropriate coin diameter and thickness are produced.

When Things Go Wrong

While it’s nearly impossible for the wrong metal to be used for blanking, there are still several ways a planchet error can slip past mint inspectors. These include:

Blank Planchets

Before having their rims raised in the “upsetting” machine coin blanks are known as Type 1 planchets. These are blanks that never make it through the preparatory process. They have rough edges and depending on what stage of manufacture they were in before escaping the mint, they may be off-color or have a grainy appearance. If they’re smooth and shiny, chances are they’re counterfeits used as slugs to fool vending machines.

Occasionally a finished planchet may not make it to the coin press or be ejected without being struck. These blanks will have a raised rim from the upsetting machine but will not have the coin design stamped on them. These are called Type 2 planchets since they’ve been through the first phase of production.

Clipped Planchets

A feeding error in the blanking machine can cause a punch to strike in the wrong place. Depending on how the metal is misfed, the clipping can take the form of a crescent shape, a smooth straight clip or a ragged straight clip. Clipping errors are often counterfeited, so look carefully at the clipped edge. If it’s a mint error the edge of the clip will show signs of the metal flowing into the clipped area. If the edge is sharp, it’s probably a fake.

Wrong Planchet

Occasionally the wrong blank will be fed into the coining press. If it’s the wrong metal, the error should be obvious, a nickel struck on a cent blank, for instance. If the planchet is larger than the intended coin, it simply won’t fit into the collar. But if a smaller planchet is struck the metal will flow under the pressure of the press resulting in a misshapen or flattened coin because the die collar doesn’t constrain the metal flow.

Another error can occur when the wrong thickness metal is fed into the blanking punch—a dime sheet into a quarter punch, for instance. The resulting planchet will be the wrong thickness and weight, producing a flawed coin.

Metal Flaws

The sheet of blank metal can be flawed, too. With most of today’s coins made from layers of multiple metals, errors can occur in the production of the sheets and rolls themselves. Dirt or other impurities can cause the layers to separate under pressure causing lamination cracks on the coin’s surface. Edges of the planchet can separate creating peeling or folding. And sometimes an entire layer of the cladding can separate, exposing the metal underneath.

Collectability and Value of Planchet Errors

A genuine error coin will nearly always be worth more than face value. But as with all collectable things, the values vary greatly based on demand and rarity.

Blank Planchets: Verifiable Type 1 blanks can sell for as much as $50. Type 2 blanks are easily verified and can bring a few dollars for lower denominations and $25 or more for larger coins like Eisenhower dollars.

The jackpot for blank planchets are the ones with edge lettering like the Presidential and Native American dollars. While blanks with reeded edges are fakes (since the reeding is produced during striking) edging is done prior to striking in a separate process making these coins extremely rare. They’re worth $100 or more but beware of fakes made by grinding and polishing the features off circulating coins.

Clipped Planchets: While one of the most dramatic of planchet errors, finding clipped planchet coins won’t make you rich. Most sell for just a few dollars with the rarer examples going for $25 and up.

Wrong Planchets: These are the stars of the planchet error coins. They’re rare but usually easy to detect since the error is generally obvious. Wrong planchet coins can range from a couple hundred dollars into the thousands. A 1977 Jefferson nickel proof struck on a dime planchet is currently offered for sale at $4,000.

Metal Flaws: Coins with metal flaws such as missing layers range from around $100 up to a thousand or more.

Collecting Error Coins

Always exercise caution when buying error coins because many types are easily faked. But there are thousands of varieties still in circulation, so if collecting them appeals to you, learn as much as you can about the subject. Books and articles are available online, and there’s an organization called CONECA devoted to the education of error and variety coin collectors. Visit their website, conecaonline.org, for more information.