Mint-made errors

The planchet, die, and striking (or PDS) classification system happens to correspond with the mintmarks of the three largest U.S. mints, Philadelphia, Denver, and San Francisco.

Labels used to identify specific categories of errors may describe the cause of the error (die crack, rotated die, clipped planchet), the appearance of the coin (wavy steps, trails, missing element) or other factors (mule, cud, brockage).

Other errors, such as those resulting from a specific die crack, form a variety, i.e., a group of coins with distinctive details or characteristics.

Accidental error coins are perhaps the most numerous, although in modern minting they are rare, making them potentially valuable to collectors.

After an upending mill adds uniform rounded rims, the disks are called "Type-2" blanks (or planchets).

[3] On such curved-clip coins, often the rim opposite the clip shows a distinctive distortion and loss of detail called Blakesley Effect.

A "split before strike" will show design on both sides of the coin, have coarse to fine striations, and will usually be weakly struck.

Modern coins can still be released with hub and die errors when the defects are too small to be seen with the naked eye.

For example, in April 2013 the Central Bank of Ireland issued a silver €10 commemorative coin in honor of James Joyce that misquoted a famous line from his masterwork Ulysses[10] despite being warned on at least two occasions by the Department of Finance over difficulties with copyright and design.

[11] Missing mintmarks, dates, and other design elements occur as the result of errors in the die or at the time of striking.

A design element may be missing because foreign matter, such as grease, plugs the cavity into which the planchet's metal would normally flow under the striking pressure.

Dies can crack during use producing jaggeds, raised lines on the surface of subsequently struck coins.

Coins struck after the break falls away have a raised, rounded, unstruck area along the edge.

These so-called die chips also appear as raised, rounded, unstruck areas on subsequently struck coins.

[14] A much rarer example is the 1892-O "Micro O" U.S. Barber half dollar, which may have come about from the brief use of a mintmark puncheon intended for the quarter.

For 19th-century coins, it is difficult to call an overdate an "error", as it resulted from intentional recycling of the die.

Lines, called trails, transfer to coins from dies made using the modern high pressure "single pressing" process.

Trails were first noted on Lincoln Memorial steps found on the reverse of one cent coins minted from 1959 to 2008.

Hard objects leave sharp outlines and, on occasion, adhere to the blank producing a coin called a "retained strike-through".

Softer objects, such as grease, can fill crevices in a die, producing a weak strike with a smudged appearance.

As a result of the mint attempting to speed up production, such a large amount of excessive grease was applied to the dies that the mintmark was obscured and therefore either nonexistent or weakened on the 1922 cents.

In the accompanying image of the blank reverse, the shadow or outline of Lincoln's profile from the obverse side of the coin is visible.

A multiple strike, also referred to as a double exposure, occurs when the coin has additional images from being struck again, off center.

The coin gives a freakish appearance as a result, and various amounts of blank planchet space are visible.

There are 1997-D, 1998 and 2000 dated Lincoln cents struck on foreign planchets, but not identified by PCGS or NGC as to the country the mintage was intended.

A wrong planchet error that sold for $5462.50 on Heritage Auctions in August 2010 is an undated U.S nickel struck on top of a 1960 Peruvian 5 centavos.

Such coins are damaged (gouged, scraped, etched, mutilated, flattened) after the final strike, either accidentally or deliberately.

Corrosion, scratches, bending, and dings can all occur to coins in circulation and sometimes may mimic mint-errors.

[3] Some types of errors, such as clipped planchets, edge strikes, and foreign object strike-throughs can be faked.

Overdates, mules, brockage, double denomination, and struck on the wrong planchet errors are often valuable.

US Lincoln cent struck off-center
U.S. dime Type 1 blank (left) and one cent Type 2 blank (right)
Clipped planchet U.S. nickel showing the Blakesley Effect near the word LIBERTY
Lamination crack on a U.S. Jefferson nickel
A 1963 U.S. Lincoln Cent with split before strike planchet error. Note the weakly struck obverse (left) and striations on the reverse (right).
A 1963-D U.S. Lincoln Cent with split after strike planchet error. Note the normal strike on the obverse (left) and lack of design on the reverse (right).
Peeled cladding on a U.S. Roosevelt dime
Partial date on U.S. cent likely caused by filled die
Doubling on LIBERTY from the 1995 doubled die U.S. Lincoln cent
A die crack is seen to the left of Lincoln's head
Broken die resulting in a "cud" atop Jefferson's head
The marks seen above the word LIBERTY on this U.S. cent were caused by the obverse die clashing with elements on the reverse die intended to impress the space between the memorial columns in the design
1993 MAD clash mark on a U.S. cent
Double punched mintmark
1999 U.S. Lincoln cent depicting wavy steps .
Great Britain dateless double obverse "mule" halfpenny Edward VII 1902 to 1910, well circulated obverse. What looks like a mint error is actually a cleverly made up double headed coin, just slightly under weight.
The reverse of that same coin was also minted with an obverse die, but on a different flan. The two obverse parts were cleverly put together from two different coins. This manipulated coin was found in Australia where it was legal tender. It could have been used in the very popular Australian Two-up game in a fraudulent way.
Because of misalignment, the obverse of this coin is off-center but the reverse is centered
This broad struck U.S. Lincoln cent is the size of a nickel
Uni-face coin (blank reverse)
Die cap
The brockage image of the Lincoln memorial can be seen near the bottom of the coin
Lincoln cent with second off-center strike
Flip-over multi-struck coin
Nickel struck on one cent planchet
U.S. Lincoln cent (obverse) with impression of a Lincoln reverse due to post-mint compression damage from a train