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The mint error type called a “double-denomination” is exactly what the names implies — two different denominations on the same coin. Such a coin will have the design of two (or more) different denominations of coins on it. A usually dramatic error type in appearance and popular with collectors, the double-denomination is known among all modern as well as older coin series.

PCGS 1964 Washington Quarter double-denomination struck on a 1964 Roosevelt Dime. This is a very scarce double-denomination type, with probably 25 to 30 known for the Washington Quarter series. Some design is visible, such as the word “LIBERTY” in the 2-4 o’clock area of the obverse. The date is visible in front of Washington’s nose. Courtesy of Jon Sullivan. Click image to enlarge.	PCGS 1980-P Lincoln Cent double-denomination struck on a Roosevelt Dime. Often called an “11c”, the Lincoln Cent struck on a Roosevelt Dime is far and away the most common double-denomination combination for U.S. coins. Courtesy of Jon Sullivan. Click image to enlarge.

How does this error type occur? In order for a double-denomination to be made, it all starts with a normally struck coin. The coin is then accidentally fed into the coining press of another denomination of coin and is overstruck with the dies. The result of this is a coin with the metal and design of the first coin, but also a second design struck over the top of it.

Additionally, the coin’s edge will exhibit the edge design of the coin being overstruck. For example, if it is a Jefferson Nickel struck on a dime, the coin will have a reeded edge because a dime has a reeded edge. If it is a Kennedy Half Dollar struck on a Jefferson Nickel, it will have a smooth edge because a nickel has a smooth edge.

Double-denominations are frequently referred to by the denominations that they are made up of, such as “11c” or “35c.” The 11c would refer to a cent struck on a dime. A 35c would refer to a quarter struck on a dime. If it is a Sacagawea Dollar struck on a nickel, it would be a $1.05. The denominations are simply added together to come up with the “new denomination.”

In the photos here, the 35c 1964 Washington Quarter is overstruck on a 1964 Roosevelt Dime. Although the design is not strong, it is visible under the quarter’s strike. Also, the coin has a fully reeded edge, which is from the dime’s reeded edge. The dime was accidentally fed into a Washington Quarter press and was overstruck with the quarter dies, making it a double-denomination error.

There are some coins that look like double-denominations in many ways but are not in fact that error type. One of them is the off-metal error, which is a coin struck on the planchet intended for a different coin series. For example, a Jefferson Nickel on a cent planchet is a cent planchet that is struck with nickel dies. The coin will have the design of a nickel but is struck on the smaller, copper planchet of a cent. The major difference which makes this coin an off-metal and not a double-denomination is that there will be no design from the cent at all on the coin.

Off-metals never have more than the one design on them, whereas double-denominations always have the design of the two (or more) different coins. There are double denominations which are actually made up of three different coin series, and so are sometimes referred to as “triple-denominations” (they are exceedingly rare!)

Another type of coin, which is commonly mistaken as a double-denomination, are coins which were intentionally overstruck—not as mint errors, but intentionally by the government. This occurs occasionally on world coins, where for one reason or another a government intentionally overstruck a previous coin design with a new coin design. Additionally, on early American coinage coins are found overstruck as well, such as on certain dates of large cents and half cents. Coins such as these are not double-denomination errors and have no premium as “mint errors” (since they are not errors at all.)

Double-denominations are known on most 20^th-century coin series and even on some 19th-century coins. However, far and away the most common types are the Lincoln Cent on Roosevelt Dime (11c) and the Jefferson Nickel on Lincoln Cent (6c.) It’s safe to say that all other double-denomination combinations are scarce. Other than the two mentioned combinations, most other combinations have less than around 25 to 50 known for the entire coin series. For example, Jefferson Nickels are known struck on Roosevelt Dimes, but they are very scarce with probably fewer than 50 known combined of proof and business strikes. Kennedy Half Dollars are known struck on Jefferson Nickels, but there are probably less than 15 known for the entire series. Because of their rarity, the only coin series that offer a large availability are the Lincoln Cent on Roosevelt Dime and the Jefferson Nickel on Lincoln Cent. This is particularly true of the Lincoln Cent on Roosevelt Dime, for which series there are probably more double-denominations known than all other U.S. coin series put together!

Collections by date can be largely accomplished for the 11c, although it would be very challenging as some years are unique or close to it. Another way to collect double-denominations is to get as many double-denomination combinations as possible, such as a 25c on 1c, 5c, 10c, etc. Collecting double-denominations is daunting, but the challenge due to their rarity, and dramatic nature of the coins makes them a lot of fun for collectors.