Generally speaking, there are two extremes in U.S. coin collecting. The first is to search for that Holy Grail coin in great condition, such as an 1856 gold Double Eagle that was minted in New Orleans and is graded AU-55, or a 1873 Morgan silver dollar, minted in San Francisco and graded MS-65.

People who love error coins are at the opposite end of the perfection spectrum, though they often pay top dollar for their treasured damaged goods. Errors are coins that didn't turn out quite as the mint intended, with clipped edges, overstruck dates, and quirky imperfections.

One of the many things that makes error coins so interesting is that they encourage the coin collector to become knowledgeable about the minting process itself, since all error coins are the result of something going awry at the mint.

At the top of the error pyramid are hub errors. The hub is the piece of hardened steel that is used to create a die, which is the metal punch that delivers a coin’s design onto a blank, or planchet. The design on the hub is the same as that on the coin, but the die is a mirror image, which means it transfers a correctly oriented image onto the final coin.

Until recent advances in minting technologies, it had taken two, three, and sometimes four strikes of a hub onto a heated die to successfully transfer the hub’s image. That left a lot of room for error, the most common of which occurs when the first and second strikes of a hub on a die are not perfectly aligned. In these cases, a doubled die is created, resulting in a coin whose elements repeat.

In rare cases, a double denomination can be created, such as in the case of the 11-cent denomination. Struck coins are sometimes transported from coining presses in bins that are later used to transport planchets. In this case, a bin full of struck dimes was reused to transport penny planchets. A few dimes that had become stuck at the bottom of a bin were struck again as cents along with all the planchets. The resulting 11-cent double denominations are larger than dimes but smaller than pennies. Coins that have the most detail are generally the most expensive, but collectors should mis-merit the value of a coin that's not perfectly round.

Another classic example of a doubled-die coin is the 1955 Lincoln Wheat penny, which some experts refer to as an error but others call a variety because so many of them made it into circulation. When the doubled die for this coin struck the obverse, or face, of the planchet, doubling occurred on the date and legend. As a result, the coin looks oddly out of focus...

Since the mistake was not caught until the coin was in circulation, no one knows for sure how many were made—just under 331 million Lincoln Wheats were minted that year, but only 15,000 doubled examples are known to exist. Whatever their number, the coin is credited with igniting an interest in error coins, as well as being a favorite target of forgers.

For collectors, only Lincoln Wheats with clearly defined doubling are considered valuable. For example, a coin with less pronounced doubling, known as a “poor man’s doubled die,” can be picked up for under a quarter, while coins whose doubling is clear and crisp sell for $1,000 and up.

Worn-out dies are also a problem. If the die is cracked, those cracks will also appear on a coin. Similarly, if a small section of the die has broken off, then a like-sized section of the coin will remain unstruck. This frequently happens along the edge of a coin and is referred to as a cud.

Even if the die is not compromised, many things can go wrong when it strikes a planchet. One relatively common occurrence is a broadstrike error, which is when the collar die (the punch that imprints the planchet with the design on the coin’s edge) fails to strike the coin at all, leaving it without any edging and a flattened-out center image.

Sometimes a die will strike a planchet wildly off center. In these situations the die is not the culprit; rather, there was a problem with the way in which the planchet was moved into position in the press. In extreme cases, an off-center coin will remain in the press to be struck a second time or more. In general, coins with multiple errant strikes are more prized by collectors than those with only one.

One of the most intriguing types of errors is a coin that has been struck properly but onto a clipped planchet, which is created when something is out of whack with the machine that stamped them out in the first place. For example, the machine stamps out a row of planchets too close to the one above it, the resulting bad blanks will look like someone took a bite out of them.

Planchet errors are also caused by stamping too close to the edge of the planchet’s source sheet metal, producing a blank whose otherwise perfect circular shapes are interrupted by straight edges on one side.

While production practices at U.S. Mints have improved in recent years, thus eliminating many of the most common historical errors, contemporary coins have not been immune to the occasional mistake.

For example, a crack in the die used to strike the reverse of the 2009 Formative Years Lincoln cent, which depicts the future president taking a break from chopping wood to catch up on his reading, can be seen at the bottom of the coin, through the second “U” in “Pluribus,” and up into the young man’s boot.

Because the crack resembles a bootstrap, this error, which may be widespread enough to be considered a variety, is known as the Bootstrap Lincoln Cent.

Even stranger are the die flaws that produced three different types of Wisconsin state quarters, all from the Denver mint, in 2004. The variations appear on the coin’s reverse and affect the number and orientation of the leaves on an ear of corn.

In the normal coin, the ear has a leaf on the left that arcs up and then down to the left. In a variation of that coin, there appears to be a second leaf below that one, rising out a wheel of cheese that sits below the ear of corn. A third 2004-D Wisconsin quarter shows that same extra leaf, only this time it is bent down and to the left. Inexplicable.

Finally there are so-called blundered dies, which refer to dies that were simply made incorrectly—unlike a doubled die, a blundered die suggests human rather than mechanical error. The most famous example of this sort of error is the 1982 dime, which was minted in Philadelphia but failed to identify itself with the “P” mint mark. An estimated 14,000 to 15,000 of these error dimes made it into circulation, which makes it a popular coin for many collectors.

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Mint Error 2008-w Reverse Of 07 Variety Burnished 1 Oz Silver Eagle Ngc Ms69 Er1795 S78 Liberty Cap Large Cent Plain Edge Icg F15 Off-center Mint Error 1c No R1955 Lincoln Cent, Doubled Die Obverse, Fs-021.8, Die 1, Anacs Graded Ms 60 Brn!1847 Braided Hair Large Cent Mint Error Off-center Pcgs Vf25 Starts 1c No Res!1955/1955 Lincoln Wheat Cent -obverse Double Die Error- Nice Uncirculated Brown2000 1Pcgs 1997 Cent On Struck Dime Double-denomination Ms-631861 G$1 Indian Princess Gold Dollar Pcgs Ms 61 Civil War IssueLincoln Penny Error Brockage Incuse1937 D 3 Legged Buffalo Nickel Pcgs Au 53 Cac Certified Key Date !!!1955 Bu Obw Penny Roll (double Die Error Year)-manufacturers Trust Of Ny1918/7 D Over-date Buffalo Five Cent Nickel Coin Ngc Very Good ~extremely Rare~Mint Error 25% Struck Off Center Indian Cent Pcgs Xf 45 1919 Lincoln Cent Off Center Nice!!1880-cc Pcgs Ms63 Plus Morgan Silver Dollar1955 Lincoln 1 Cent Double Die Pcgs Au 55 €Ngc Ms 66 2004 Wisconsin State High Leaf Error Quarter Edge View Slab Ms66 UpNgc Ms 66 2004 Wisconsin State High Leaf Error Quarter Edge View Slab Ms66 Up LHuge Reverse Cud - Bu 1993 Lincoln Cent - From Cherrypickercoins - 23121942 ~ 42 Over 41 ~ Mercury Dime {{ Key Error }}1952 D Lincoln Cent Off Center Nice!!1972 Lincoln Cent-double Die Obverse! Smooth Red/brn Well Struck Surfaces-choice1937-d Buffalo Nickle 3-legged Error Coin1811 Mexican 8 Reale War Of Independence Chihuahua Cast Plain Edge ErrorNgc 1980-p Nickel On Cent Planchet Ms-63 Rb1866 Indian Head Cent Scarce~double Die~misplaced Digit Fs-101, Ddo-001, Mpd-001 Nickel Rare Brockage Capped Die Error 1942 Over 1 (1942/1) "error" Mercury Dime - Very Rare Error - Great ConditionError Nickel Struck On Penny Planchet 1970 D Jefferson On Copper Penny 3.1 Grams1997 1L@@k....1975-d Lincoln Cent - Huge Obverse Cud - No Res! 23. A 1972 D Jefferson Nickel Struck W/ Curved Clip Error / Fragment? 2.2gr1957 D Lincoln Cent Off Center Nice!!Large Coin Collection Of Error Pennies 1913 To 1960 In Metal Box, 279 Pennies1955 D Lincoln Cent Off Center Nice!!2007 G. Washington $1 Missing Edge Lettering Pcgs Ms-661977-d Missing Clad Layer Obverse 25c Error Coin - Stunning Red Color!1921 50c Pilgrim Ngc Ms64 Silver Commemorative Double Clashed Rev. Nice Luster 1924 $20 St. Gaudens Gold Coin - Ngc Ms 6340% Silver Planchet Ike $1 Experimental Rinse1976-d Ike $1 €Indian Head Penny 1859 Error? Odd Strange CoinVery Rare!! Huge Clip Huge Broadstrike 1993-p Roosevelt Dime Mint Error Coins1887 Top 100 Morgan Dollar Ddo Gator & Clash Vam 12a Ms62 Ngc Double Die Obverse2001-d Lincoln Cent Double Strike With 2 Full Dates And Rare Die Struck Reverse1979-s Sba $1 Struck-thru Grease2009-s Puerto Rico 2520 Pcs. Error Coin Lot1883-o Morgan Dollar -ngc Fitzgerald- Error Vam 52 R5- Tilted O, Dbl Ear + More!Clad Eisenhower Dollar Blank Planchet (type2) Mint Error Pcgs Ms 6022. First Found 2014 P Jefferson Nickel Struck With Curved Clip Error! Nr11. A 1999 D Pennsylvania State Quarter Struck W/ Triple Clip Error1935 Buffalo Nickel F15 Pcgs Ddr Fs-801 Die 1 Double Die Reverse CherrypickerMis-labeled 2000 Ngc Ms-70 Library Of Congress Silver Dollar Yellowstone LabelUnsearched Estate Cent Roll Error Blank Cent Planchet / Vf 1903 Indian Head Sh1937 50c Reeded Edge Half Dollar Choice Au Mint Error13. Sold As Is * 86 Mint Error Blanks * Damaged Dimes, Sba Dollar, Cents, Nickel1983 Doubled Die Reverse Lincoln Memorial Cent Error Pcgs Ms64rd Double1867 Shield 2 Cents -double Die Error- Fs-101, Die-1 About Uncirculated1798 Large Cent Error Clipped Planchet Vg+