Struck-Through Error

What it is

A struck-through error occurs when something sits between the die and the planchet during the strike. Grease, cloth, wire or another coin can leave an impression or block part of the design.

What causes it

Foreign material on the die face or planchet. Grease-filled dies are the most common cause.

How to identify it

• Missing or weak design elements where grease filled the die.
• Texture or shapes pressed into the coin's surface.
• The missing area has the same surface as the rest of the coin, not scratches.

How to tell it from damage

A worn or damaged coin shows scratches and irregular wear. Grease strikes are common and usually carry small premiums, while dramatic struck-throughs can be valuable.

What gets between the die and the planchet

A coin press runs fast and the coining chamber is surrounded by lubricated machinery, conveyors and bins of blanks. Anything that ends up on the die face or on top of the planchet when the dies close is struck into the coin. Grease and oil mixed with fine metal dust, often called die fill, is by far the most common. Other materials include cloth and rag fragments, wire, staples, thread, bristles, metal fragments and even another planchet.

Grease collects in the small, narrow recesses of the die, such as letters, numerals and the mint mark. Once a recess is packed full, planchet metal cannot flow into it, so the struck coin shows that element weak or missing. A die can strike many coins in this state before the fill works loose or the press is cleaned, so grease strikes often come in runs from the same die.

Kinds of struck-through errors

Collectors sort struck-throughs by what was in the way. Struck through grease shows soft, mushy or missing design elements. Struck through cloth shows a fine woven texture pressed into part of the coin. Struck through wire or thread shows a curved or straight sunken line with a rounded bottom. Struck through a metal fragment shows a sharp-edged depression in the shape of the fragment. When the object stays embedded in the coin, the error is called a retained struck-through.

A planchet that lies on top of another blank during the strike produces a related error called an indent, where the lower coin shows a smooth, round depression the size of the upper blank. Struck-throughs can affect either side of a coin and can combine with other errors.

Famous struck-through coins

The 2005-P Kansas state quarter known as In God We Rust is the best-known grease strike of modern times. Grease filled the T of TRUST on an obverse die at Philadelphia, so the motto on coins from that die reads IN GOD WE RUST. Coins from the same die show the missing letter to different degrees as the grease came and went.

Grease-filled letters show up on cents, nickels and quarters of every modern date. Some, such as Lincoln cents with letters missing from LIBERTY, are collected as a group even though they are not separate die varieties.

Examining a struck-through error step by step

Start with the surface inside the affected area. A struck-through area was formed under full striking pressure, so it has smooth, unbroken metal, though it may lack luster. Look for texture: a cloth weave, the twist of a thread or the rounded profile of a wire are all clues to what was in the way.

Then check the edges of the affected area. On a grease strike, design elements fade gradually into the filled area. On a struck-through object, the depression has smooth walls with no raised burrs. Finally look at the rest of the coin. The design around a genuine struck-through is normal and undistorted and the other side shows no matching damage.

Why after-mint damage looks different

A coin pressed against an object after leaving the Mint is pushed into it at far lower pressure than a coinage press delivers and with no collar around it. The design around the impression gets flattened or bent, the displaced metal rises in burrs at the edges of the mark and the original design inside the mark is often faintly visible, because it was there first. A genuine struck-through has no original design inside the affected area, because the obstacle kept the die from ever forming it.

Missing letters from wear are another trap. Wear removes the highest points of the design first, such as the cheek and hair on a portrait, while grease usually fills narrow recesses such as letters, which wear slowly because the rim protects them. A coin with sharp hair and a missing letter suggests grease. A coin worn smooth everywhere with weak letters is simply worn.

Grading struck-through errors

Grading services attribute dramatic struck-throughs such as cloth, wire, retained objects and large fragments, often describing the material on the label. Light grease strikes are so common that most are not attributed individually. Collectors judge struck-throughs by how clear and recognizable the obstacle is, how much of the coin it covers and whether it creates a named effect like the Kansas quarter.

Frequently asked questions