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Coins struck from rusted dies show corrosion detail
Metal flows into die’s damaged areas
By Paul Gilkes

Among coinage struck in the first century of the U.S. Mint's full-scale operations, beginning in 1793, it is not uncommon to encounter coins struck from dies that rusted because of improper storage.

Some coins were struck for circulation from those rusted dies.

Other pieces exhibiting rust contamination were struck as restrikes at dates later than the date on the coin, using uncanceled dies sold by the Mint as scrap metal.

Examples of U.S. coins and restrikes produced from rusted dies are known for gold, silver, copper and copper-nickel issues from the 18th and 19th centuries.

Damaged dies

Coins struck from dies that are even slightly rusted will exhibit evidence of the rust despite efforts to remove the rust from the die or dies before striking.

The most commonly encountered evidence is the often pebbly surface that will be on the coin in the areas where the rust occurred on the die. Sometimes, the rust evidence will appear in large patches, depending on the severity of the die corrosion.

In some instances, die technicians attempted to polish away the corrosion. However, evidence of the corrosion often remained around the design periphery, and in and around the digits in the date and lettering.

Rust represents the remnants of corrosive action of atmospheric contaminants on improperly stored dies, effectively eating into and pitting the die surfaces.

When a coin is struck with a rusted die or dies, the planchet's metal will flow into the rust-eaten areas of the die, leaving raised bumps or patches on the coin during the striking process, giving that area on the coin a dull, flat appearance.

Coins known to have been struck with heavily rusted dies exhibit greater evidence of the corrosion, especially copper half cents and large cents.

Although suitable die steel was always at a premium in the late 18th century and throughout most of the 19th century, one would think it would be requisite to protect the finished dies from any handling or foreign agents that could affect their usage.

Such was not always the case, Walter Breen notes in his Complete Encyclopedia of U.S. and Colonial Coins.

Protecting the dies

Production during the earliest years of the U.S. Mint's coin-making operations was fraught with perils, most notably the annual yellow fever epidemics that often plagued Philadelphia.

According to Breen, Mint operations often ceased from August or September into late fall while Mint personnel fled the city and the yellow fever threat.

Before departing, Mint employees would place dies into storage and make an effort to properly store them.

The usual procedure, according to Breen, was to seal all dies in hot fat or similar lubricant for storage during the production impasse.

All dies would then be stored at the Philadelphia Mint or the nearby Bank of the United States before their next use.

In the haste to escape the yellow fever's annual threat, though, the possibility existed that not all dies received proper sealing treatment, or any treatment at all, Breen explains.

After the fever threat was over, Mint personnel would return to the city to resume coinage production.

If dies had rusted in the interim, they still may have been judged acceptable by Mint employees.

It wasn't the Mint's practice to indiscriminately discard dies, even if rusted or slightly cracked, if suitable production life was still left in them, according to Breen.

Back in service

"Each winter, the old dies, or all that could still be even briefly used, were retrieved from the vaults, degreased and hastily combined in any convenient pairings to make many small batches of cents," according to Breen.

Similar procedures were followed to ensure the protection of the die faces of all coinage dies, regardless of the denomination or metallic composition of the coinage to be produced.

Regardless of those efforts, though, coins struck from rusted dies are known for all denominations and compositions at least during the first century of Mint production, with scattered examples occurring during the early 20th century.

An example of a coin that can be found struck from extremely rusted dies is the 1876-CC Seated Liberty dime.

Other notable examples can be found within the Liberty Cap cent series, 2-cent series, Shield 5-cent coin series, Capped Bust quarter dollar series, Indian Head gold $3 coin series, Coronet gold $5 half eagle series, Morgan dollar series and the 20th century Peace dollar series.

The extent of the rust on some of the dies is such that resultant coins struck, not all or for all denominations, have an almost matte finish.

Preventing dies from rusting continues to be important for the U.S. Mint today.

Maintaining the dies is a huge task; the number of dies, combined, used by each of the four Mint production facilities – Philadelphia, Denver, San Francisco and West Point – totals in the thousands annually in the 21st century.

In the earliest days of the U.S. Mint, some issues were produced with a total number of dies that could be counted on fingers and toes.

Die maintenance today

More care is taken today to ensure that dies are properly stored, and if there are problems, that damaged dies are removed from service.

"Dies are stored in temperature and humidity controlled vaults, and the face of the dies is protected during shipment with protective soft caps and light lubrication to prevent damage and rust," according to a Nov. 13 statement released by U.S. Mint spokesman Michael White.

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