What it is
A die clash happens when the obverse and reverse dies strike each other with no planchet between them. Parts of each design transfer to the opposite die and appear faintly on later coins.
What causes it
A feed failure left the coining chamber empty while the press cycled.
How to identify it
- Faint outlines of the opposite side's design appear on the coin.
- Common examples are column lines from the Lincoln Memorial showing on the obverse of cents.
- The marks are raised.
How to tell it from damage
Scratches or toning patterns can look like clash marks. Clash marks follow the exact shape of the other side's design.
Famous examples
How dies clash in the press
Each press cycle normally delivers a planchet between the dies just before they close. If the feed fails to deliver one, the dies come together with nothing between them and meet face to face at full force. The edges of each die's design press shallow outlines into the face of the other die.
Those outlines are sunk into the die, so every coin struck afterward shows them as faint raised lines. The clash marks stay on the die until it is retired or polished to remove them, which means a single clash can mark thousands of coins. A die can also clash more than once, stacking several sets of marks on top of each other.
Clash marks are found on coins from the earliest days of the US Mint to the present. Large, fast production runs give plenty of opportunities for a feed to miss, so even modern dies show light clashes.
Where clash marks appear on common series
On Lincoln Memorial cents struck from 1959 to 2008, the most familiar clash puts traces of the Memorial's columns and steps in the field around Lincoln's neck and the back of his head. On the reverse of clashed cents, part of the outline of Lincoln's head can sometimes be traced in the field near the Memorial.
On the Franklin half dollar, the 1955 Bugs Bunny variety shows clash marks from the eagle's wingtips on the reverse appearing in front of Franklin's mouth as two small lines that resemble buck teeth. Morgan dollars, Indian Head cents and Barber coins also show clash marks often. Specialists in those series catalog clashed dies along with other die varieties.
Clash marks and over-polished dies
When clash marks were noticed, Mint workers often removed them by polishing, or lapping, the die face. Polishing takes off a thin layer of steel and can erase fine design details along with the clash. The famous 1937-D three-legged Buffalo nickel was created this way: a Denver die was polished to remove clash marks and the buffalo's front leg was polished away with them.
A clash is therefore sometimes the first chapter in a longer die story. Collectors who study die states look for clash marks on early coins from a die and polish lines or missing details on later ones.
Reading the shape of clash marks
Clash marks are not random. They follow the outlines of design elements from the other side, in the position those elements held when the dies met. Because US coins are struck with a fixed alignment between obverse and reverse, clash marks show up in predictable places: on a Memorial cent, the central columns line up behind Lincoln's head.
Clash marks appear as if you were looking through the coin at the other side, so lettering in a clash reads backward. Strength varies. A single hard clash gives bold, clear outlines, while repeated light clashes leave faint, overlapping lines.
Checking a coin for clash marks step by step
Hold the coin under a single light at a low angle and rotate it slowly. Clash marks show up best as the light rakes across the field. Look in the areas where the opposite design would fall if you could see through the coin. Compare the shapes you find with the actual design on the other side. The lines should match the outlines of specific elements, such as columns, letters or the edge of a portrait.
Next confirm that the lines are raised. Clash marks formed in the die, so they stand up from the field and carry the same luster as the rest of the coin. If you are searching a roll, set aside any coins with matching marks. Coins from the same clashed die will show the marks in exactly the same place.
Clash marks compared with damage and toning
Scratches and hairlines are cut into the coin and run in straight or random lines that do not match any design element. Toning can form streaks that look like outlines but has no relief. Tilting the coin under light shows that the color lies flat on the surface. Clash marks are raised, shaped like real design elements and found in the same place on every coin from the clashed die.
Frequently asked questions
What causes a die clash?
A feed failure left the coining chamber empty while the press cycled.
How can I tell a die clash from damage?
Scratches or toning patterns can look like clash marks. Clash marks follow the exact shape of the other side's design.
Do clash marks make a coin valuable?
Light clash marks usually add little, but strong, clear clashes and named varieties such as the 1955 Bugs Bunny Franklin half carry premiums. The premium depends on how bold the marks are and whether the die is listed.
Why does my penny have lines behind Lincoln's head?
Lines behind Lincoln's head on a Memorial cent are often clash marks from the Memorial's columns, transferred when the dies struck each other. Check that the lines are raised and match the shape of the columns.
What causes a die clash?
A die clash happens when the press cycles without a planchet between the dies, so the dies strike each other. Each die picks up an outline of the other's design.