Pictures Of Penny Die

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All coins struck in the United States are struck by a pair of dies. A die is a steel rod with a face that is the same size as the coins that it will be striking. This steel rod will contain the design for one side of the coin. Two of these steel rods (dies) are needed to strike coins. One will have the obverse (front of the coin) design, and the other will have the reverse (back of the coin) design.

The dies are set up in a machine called a coining press so that a planchet (blank) will come between them. In the older coining presses one die would be positioned above the other. The upper die (hammer die) would come down with great force and strike the planchet while it was resting on the lower die (anvil die). The force of the hammer die striking the planchet on the anvil die would place the images from the dies onto the planchet and the result would be a coin as we know it. In the newer coining presses the action of the hammer die is now side-to-side rather than up and down, but the process is still essentially the same, as is the result.

The reality is that the die varieties we enjoy collecting, which includes doubled dies, repunched mint marks (RPMs), over mint marks (OMMs), repunched dates (RPDs), overdates, (OVDs), and misplaced dates (MPDs), are the result of mishaps that occur in the process of making the dies that strike the coins. A working knowledge of the die making process will help us to see how the various die varieties resulted over the years. The technology for making U.S. coinage dies has evolved significantly over the years. Because of these technological advances, most of the die varieties that we enjoy collecting will never be produced again. The only die variety that the Mint has had difficulty eliminating is the doubled die, and we will have more on that later.


In the earliest days at the U.S. Mint, from approximately 1792 through 1836, a Master Die for a given year and denomination was produced by a Mint engraver who carved the central design for a coin directly into the face of the master die. The design elements around the edge of the coin such as the mottos, stars, and date were not carved into the master die. The carved design was cut out of the face of the master die so it was recessed (incuse) on the face of the die.

This master die is not used to strike coins. Because of the number of coins for a given denomination that need to be struck in any given year, it was not feasible to use these hand engraved dies to actually strike coins. Using modern coinage as an example, in 1996 the Philadelphia Mint produced about 6.6 billion Lincoln cents. The average life of a Lincoln Cent die is about 1 million coins. Some simple math will tell us that in 1996 the Philadelphia Mint alone would have needed about 6,600 Lincoln Cent dies to strike the Lincoln cents produced that year. Of course in the earlier days of the Mint that we are examining here, the yearly mintages were much less than modern mintages. However, the life of a die was also much less than that of modern dies, so it was still very impractical to hand engrave the dies that would strike the coins.

Rather than being struck by the master die, coins are struck by Working Dies. The master die is used as a tool from which the working dies would ultimately be produced. When the engraver was finished carving the central design into the master die, the master die was taken to a machine known as a hubbing press. In the hubbing press the master die was placed above a blank steel rod. With great pressure the face of the master die was lowered and squeezed into the steel rod leaving the impression of the image on the master die on the face of the steel rod. The blank steel rod has a cone-shaped face to allow for easier metal flow into the recessed areas of the die when the pressure from the hubbing press is applied. The new steel rod is known as a Working Hub and it now has the design images in relief (raised) just like on the struck coins. The face of the working hub looks exactly like one side of a struck coin.



These blank steel rods with cone-shaped faces (tops) are used by the Mint in a hubbing press to create master dies, working hubs, and working dies.



This photo illustrates a working hub that was created for the Lincoln Cent reverse. If you look carefully, you can see that the images on the face of the working hub are raised and look just like they will appear on the struck coins. The arrows point to grooves along the edge of the hub. They allow for proper alignment of the working hub and the working die when more than one hubbing is needed to complete a satisfactory image on the hub or die being made. The corresponding dies will have raised areas (lugs) in the same locations that fit into the grooves to insure proper alignment.