What it is
As dies wear, they crack. Metal flows into the crack during striking, leaving a raised line on the coin. When a piece of the die breaks away at the rim, coins show a raised, featureless blob called a cud.
What causes it
Metal fatigue from millions of strikes.
How to identify it
- Die cracks are thin, raised, often wandering lines.
- Cuds are raised lumps along the rim with no design detail.
- The same crack appears on every coin from that die at that stage.
How to tell it from damage
Scratches are cut into the coin. A die crack is always raised.
Famous examples
Why coinage dies crack
A coinage die is hardened steel, but every strike drives it into the planchet with great force. Over hundreds of thousands of strikes that repeated stress opens tiny fractures. Cracks usually start where stress concentrates: at the rim, along the edges of deep design elements and between closely spaced letters. Once a crack opens, each strike forces a little planchet metal into the gap, so the crack shows up on coins as a fine raised line.
Cracks grow with use. A die that began with a short crack between two letters can develop a crack that runs across the whole face and links up with others. If two cracks meet and isolate a piece of the die face, that piece eventually loosens and falls out. When the missing piece includes part of the rim, coins struck afterward show a cud.
Better die steel, heat treatment and planned die retirement mean modern dies are usually removed before they fail badly, but cracks and cuds still turn up regularly on modern cents and quarters.
Die states and the language of die breaks
Specialists track a die's life by its die state. An early die state coin shows a fresh die with sharp detail and few or no cracks. A middle die state shows cracks starting to form. A late or terminal die state shows long cracks, die breaks and sometimes cuds just before the die was pulled. Because each coin captures the die at one moment, a group of coins from the same die can be arranged in order to show how its cracks grew.
Die chips are small pieces that break out of the die face and leave raised dots or blobs, often inside letters. Die breaks are larger pieces lost from the die face. A cud is a break that touches the rim, while a break that stays inside the design is sometimes called an interior die break. A retained cud is a break where the piece cracked loose but stayed in place, so coins show a raised step along the crack while the design in the broken section is still present, slightly out of line.
Well-known cracks and breaks
The 1999-P Delaware spitting horse quarter shows a die crack running from the horse's mouth, so the horse appears to be spitting. Wheat cents of the 1950s are known for BIE errors, die breaks between the B and E of LIBERTY that look like an extra letter I. Morgan dollar specialists record many cracks and breaks in the VAM catalog, named for its authors Leroy Van Allen and A. George Mallis. They collect these varieties die by die.
State quarters, Lincoln cents and Jefferson nickels have produced many rim cuds, some large enough to cover a letter or two of the legend. Because each cud comes from one die at one stage of its life, collectors often record the exact position by clock direction and the letters it touches.
How metal flows into a crack or cud
Planchet metal is driven into every recess in the die, which is how the design is formed in the first place. A crack is just another recess, so it fills too and the coin shows a raised line that follows the crack exactly. A cud is a large, flat-bottomed hole at the edge of the die. The planchet flows into it and forms a raised lump with no design and a slightly grainy top that reflects the broken die surface.
Because so much metal flows into a large cud, the area on the opposite side of the coin directly behind the cud is often weakly struck. The metal that should have filled the other die's design went into the cud instead. A weak area opposite a cud is a good sign the cud is genuine.
Examining a die crack or cud step by step
Use a 10x loupe and tilt the coin under one light. A die crack should cast a small shadow on both sides, showing that it stands above the field. Follow it from end to end. Genuine cracks wander irregularly, often from the rim toward the design or from letter to letter. They pass over raised design elements as a continuous raised line.
For a cud, confirm that the lump rises to about rim height or above, that its surface is granular rather than smooth or molded, that its border with the design is sharp and that it merges with the rim on either side. Then check the other side for weakness behind the cud. If you can find another coin from the same die, compare them. The crack or cud will be in exactly the same spot.
Telling cracks and cuds from damage
A scratch is the opposite of a die crack. A tool removes or pushes metal aside, leaving a groove with raised lips along its sides. Under magnification a scratch has a bottom, while a die crack has a top. Glued or soldered blobs sold as cuds sit on top of the coin's surface and show a joint line, a different color or a shiny or bubbly texture. The coin also shows no weakness on the opposite side.
Frequently asked questions
What causes a die crack and die break?
Metal fatigue from millions of strikes.
How can I tell a die crack and die break from damage?
Scratches are cut into the coin. A die crack is always raised.
Is a die crack on a coin valuable?
Most small die cracks add little or nothing, but large dramatic cracks, die breaks and especially cuds carry premiums. Famous cracks such as the spitting horse quarter are collected by name.
What is a cud on a coin?
A cud is a raised, featureless lump along the rim, caused when a piece of the die's edge broke away. Metal filled the gap during striking.
What is a retained cud?
A retained cud is a die break where the broken piece stayed in the die, so the coin shows a raised step along the break but keeps its design in that section.