What it is
A brockage is a coin that shows a mirror-image, incuse design on one side. It happens when a coin that was already struck sticks to a die and acts as a die itself.
What causes it
A struck coin stayed on one die and pressed into the next planchet.
How to identify it
- One side shows a backward, sunken version of the design.
- The incuse side is often expanded and soft.
- Partial brockages show the effect on part of the coin only.
How to tell it from damage
Damage that presses one coin into another can mimic a brockage. Real brockages show even metal flow.
How a struck coin turns into a die
After each strike, the coin is supposed to be pushed out of the collar and swept away by the feed fingers. Occasionally a struck coin sticks to one of the dies instead, held by grease, suction or friction. When the next planchet arrives, the dies close again and the stuck coin sits between that die and the new blank. The stuck coin's raised design is pressed into the blank, leaving a sunken image, while the other side of the blank is struck normally by the opposite die.
Because the image comes from a coin rather than a die, it reads backward, just as a seal reads backward when pressed into wax. It is also softer and wider than a normal design, because the stuck coin flattens and spreads a little more with each strike.
Why a brockage shows the same design on both sides
Think through what touches the new blank. A coin stuck to the reverse die has its obverse facing the incoming planchet. The obverse die strikes the planchet's top normally, while the stuck coin's obverse presses into its bottom. The result is a coin with a normal obverse on one face and an incuse, mirror-image obverse on the other. It has no reverse design at all.
This makes the classic full brockage easy to recognize: the same design appears on both sides, raised and readable on one, sunken and backward on the other. Collectors name the brockage by the design that appears incuse, so an obverse brockage shows the incuse obverse.
Full, partial and capped die brockages
A full brockage covers the whole face. A partial brockage happens when the stuck coin only partly overlaps the new planchet, so only part of the face shows the incuse image and the rest shows normal design or plain field. Partial brockages are more common than full ones.
If the stuck coin stays on the die for many strikes, it is hammered into a cup shape that wraps around the die face, called a die cap. Coins struck by a die cap show a brockage that grows larger, thinner and more distorted with each strike, until the image becomes an indistinct outline. These are called capped die strikes. Die caps that escape the Mint are prized by error collectors.
A mated pair is a brockage and the coin that made it, found together and matched by their marks. Mated pairs are rare. Brockages exist on every denomination but are found most often on cents, the coin struck in the largest numbers.
A step-by-step brockage check
Read the incuse side first. Letters should be backward and sunken and the design should match the design on the coin's other face. Then check the edge and size. A brockage struck inside the collar has a normal diameter and edge, reeded if the coin should be reeded. Its weight is normal too.
Look at the quality of each side. The normal side should be sharp with full luster, because a real die struck it. The incuse side should be smooth with soft but continuous detail, often with a broad, flattened border where the stuck coin's rim pressed in. Any tool marks, distorted lettering on the normal side or a bulging edge point to an alteration.
Why pressing two coins together does not make a brockage
Brockages are sometimes faked by placing two coins together and squeezing them in a vise or hydraulic press. That does push a sunken image into one coin, but it also squeezes the normal side of that same coin against the other jaw of the press, flattening its design and spreading the coin out of round. Without a collar, the edge bulges and any reeding is crushed.
A genuine brockage received its normal side from a real die in the same blow, inside a collar, so that side is crisp and lustrous and the edge is normal. The incuse side also shows even metal flow across the whole image rather than the uneven pressure of a homemade squeeze.
Grading and collecting brockages
Grading services attribute full and partial brockages, often noting the percentage for partials, as well as capped die strikes. Full brockages with a clear incuse image are the most desirable. Because the incuse side is soft by nature, collectors judge a brockage on the clarity of its incuse image and the quality of its normal side rather than by grade alone.
Frequently asked questions
What causes a brockage?
A struck coin stayed on one die and pressed into the next planchet.
How can I tell a brockage from damage?
Damage that presses one coin into another can mimic a brockage. Real brockages show even metal flow.
What is a brockage coin?
A brockage is a coin with a normal design on one side and a backward, sunken copy of a design on the other. It forms when a struck coin sticks to a die and is pressed into the next blank.
Why is the design backward on a brockage?
The incuse image was pressed by a coin rather than a die, so it is a mirror image, the way a rubber stamp reads backward. Real dies carry a reversed design so that coins read correctly.
What is a die cap?
A die cap is a struck coin that stayed on a die for many strikes and was hammered into a cap shape. Coins it strikes show increasingly distorted brockage images.