A doubled image on a coin can often greatly increase its value.
Let’s look at the terminology used. Per the U.S. Mint, a “die” is defined as:
Die: An engraved stamp used for impressing a design (images, value, and mottoes) upon a blank piece of metal to make a coin.
So, on a double die coin, the images on the coin appear more than once.
To be clear, there are two types of doubling that can occur in coins. One is called a “double die” and the other is referred to as “strike doubling”. I will go over these separately.
This instance of a double die coin is illustrated perfectly in the 1955 wheat cent.
You can see that the mottoes and date are stamped on the coin twice. So, how does something like this happen? Below is an account regarding this cent in particular.
“It is extremely rare that such dramatic doubling would slip through unnoticed at the US Mint. At the time, the Philadelphia Mint was running two 12-hour shifts in order to help alleviate a cent shortage. At least seven people were supposed to have inspected the die before it was put into use, but that clearly was not the case here. Instead, the die was placed in service for a midnight to 8:00 am shift. The problem was not discovered until some 20,000-24,000 cents had already been mixed in with the millions of other cents struck that night. The Chief Coiner of the Philadelphia Mint, Sydney C. Engel, decided to let the coins through instead of melting a total of approximately 10 million cents to contain them” ~ NGC (Numismatic Guaranty Corporation)
I will detail here how double die coins occur in the coin making process. The “hub” is the first part of this process. It is a rod of metal with the artwork for the future coin cut into the end of it. When you look at the hub, the artwork looks the same as what the eventual coin will look.
Using the hub, a die is made. When the die is made, it’s features look exactly opposite of what the future coin will look like.
The doubling error occurs when the die is struck by the hub. The die is defective. Thereafter, every coin struck from that die has the doubled features.
The other form of doubling is called “strike doubling”. It has other names too, such as “machine doubling”. This type of doubling takes place later in the coin making process. It occurs when the die actually hits the disk that will become the coin. This disk is called a “planchet”.
“. . . this type of doubling occurs when the die strikes a planchet. If the die is not properly seated, it can move slightly or bounce during the moment of striking, creating a flat, shelf-like doubling.” ~ NGC
Look inside the lettering. You will see the machine doubling. There is an extra “lip” or “shelf” inside the letter “O”. You can see this clearly on the outside of the “S” and also on the outside of the “F”.
DOUBLE DIE COINS AND THE COLLECTOR
Doubling can greatly increase the value of a coin. But, one shouldn’t consider that it always indicates greater value. Not every doubling on a coin is valuable. During World War II, for example, many coins had doubling. They were short on materials and were under pressure to produce a lot of coins. As a result, there are many of these errors (and others). The doubling and other errors on these coins doesn’t always indicate greater value.
The thing to do when reviewing the coins that you have which show doubling, is to look and see what similar coins have sold for on eBay, coin magazines and other sources. Maybe, you’ll find a treasure. Maybe it will just be an interesting looking coin. But, it can be worth looking!