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Double-Struck Mint Errors

By Jon Sullivan for PCGS ……
A very popular mint error type is the double-strike. It is dramatic in appearance and easily understood. Some of the most valuable mint errors are double-struck coins. Double-strikes are found on the earliest ancient coins all the way up to the modern-day coinage. Because of how coins are made (being “struck” with dies), it’s an error type that will likely always be with us – and that’s a good thing!

As the name would suggest, a double-strike is a coin that is struck “twice”. The double-struck coin typically will be struck correctly on the first strike, but then will be struck again either on-center or off-center. A double-struck coin is one that has just been struck twice, but the number of times a coin can be struck is infinite, and some coins are known with over 100 strikes on them.

Let’s talk about the four primary double-struck types: the double-struck off-center, the double-struck on-center, the multi-struck, and the flip-over double-struck.

Double-Struck Mint Errors

A double-struck off-center coin is one of the most common types of double-struck errors. Courtesy of Jon Sullivan

The double-struck off-center occurs when a coin is struck and then fails to be fully ejected from between the dies before being struck a second time with the strike off-center. Above, we see an example of a double-strike with the second strike off-center. This is the most common of the double-strike types.

Double-Struck Mint Errors

The double-struck on center shows the second strike virtually on top of the primary strike. Courtesy of Jon Sullivan.

Double-strikes on-center generally occur when a coin is struck, fails to be ejected from the collar die, and is struck again with the second strike directly on top of the first strike. Oftentimes, double-strikes on-center will be rotated between strikes, with the first strike not perfectly aligned with the second strike.

Multi-strikes carry at least three strikes but can bear potentially an infinite number of strikes. Courtesy of Jon Sullivan.

A multi-strike is a coin with three or more strikes. Multi-strikes can be either on-center or they can be off-center, but in order to qualify as a multi-strike, the coin must have at least three strikes present. It is not uncommon for a coin to be struck four or five or more times, although generally the more strikes a coin has the scarcer it will be.

Why do double-strikes occur at all? Usually, it’s because there is something not working correctly with the coin press’ ejection system, and the feeder finger (which is what puts planchets between the dies and ejects them from the die) is not working correctly; it fails to eject the struck coin from between the dies. When this happens, the dies strike the coin a second, third, or more times until either the coin is ejected or a mint employee notices the press is not functioning properly, stops the press, and fixes whatever the issue is.

Back before the striking of coins was fully automated, planchets were hand fed into the presses, and if a struck coin was not quickly grabbed by the press worker, the dies might come down a second time and give the coin another strike.

There are many variations and combinations of double-strikes, which are too numerous for the purposes of this article. However, one of the most common terms used with double-strikes is the term “uniface”, which means that one side of the strike occurred with another planchet blocking the strike, keeping it from receiving a normal strike on that side. This is less desirable than a coin struck on both sides. A coin which is struck on both sides is termed “die struck both sides”. Double-struck coins that are die struck on both sides are usually worth 25-100% more than uniface coins.

Flip-over double-struck coins are among the scarcest of this category of mint error. Courtesy of Jon Sullivan.

Another often-found variation is the flip-over double-strike. This type of double-strike occurs when the coin is struck then flips over and is struck again. These are much scarcer than regular double-strikes, as it takes an unusual set of circumstances for a coin to flip over between strikes. Flip-over double-strikes usually are worth 50-100% more than regular double-strikes that did not flip over.

Doubled dies are sometimes confused with double-strikes by new collectors, but they are not related. Visually, doubled dies and double strikes have some similarities at a glance, but that is where the commonality ends. A doubled die is a variety, meaning it is a variation on the die itself. The doubled die “mistake” is in how the die was created.

Double-Struck Mint Errors

The 1955 Doubled Die Lincoln Cent is one of the most famous of all doubled dies. Courtesy of PCGS TrueView.

A die goes through a hubbing process, in which a hub (raised image of the design) is pressed into a blank cylinder of steel to become a die. This is usually done multiple times in order to create the sunken design of the coin in the die. If there is a slight shift between hub impressions into the die, or if there is any sort of movement in the designs during the hubbing process, a doubled die will result. Any coins struck from that die will then show that doubled image. Double strikes, on the other hand, occur (as described earlier in this article) as a result of the die striking the planchet more than once. Although similar, these are two totally different mint mistakes.

Collecting double-strikes can be done by getting an example of each type of double-strike, or simply by collecting a double-strike for each date for a series of coins (for example, finding a Lincoln Memorial Cent with a double-strike for each year from 1959 through 2008). Some coin series, particularly those that are made of a precious metal such as silver or gold, are usually very scarce with double-strikes. Finding a double-struck silver Washington Quarter (1932-1964) is difficult, and very few are known. Gold coin double-strikes are very rare, and only a handful are known on U.S. coins. Copper, clad, or similar inexpensive metals are much more common with double-strikes and are the best choice for a collector on a budget.

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