A few months ago I mentioned that one of my earliest collecting interests had been error coins, and while I no longer collect them (except in the form of Honduran die varieties), I do still find them interesting, and sometimes I just do find them, period!

This Summer a fellow coin dealer asked my help in attributing an odd-looking 1944-S quarter he had acquired in a collection, that he thought had been struck on a silver dime planchet. Such wrong denomination errors are decidedly scarce, but are known for most series. The closer in size the two denominations, such as cent on dime or five cents on one cent, the greater the chance the various feed mechanisms will accept the errant blank.

However, the coin did not appear to be silver, as a 1944 dime planchet would be, and I eventually discovered after performing weight and specific gravity tests that it was a truly remarkable transitional error, a 1944-S Washington quarter struck on a Steel Lincoln cent planchet left over from 1943! As the acid test I also checked to see if it stuck to a magnet. It did.

Although half a dozen or so 1944 cents are known to have been struck on leftover Steel cent planchets, just as their more famous cousins the 1943 "copper pennies" were struck on leftover 1942 Bronze blanks, a wrong denomination error in steel from the San Francisco Mint is, to the best of my knowledge, unique.

What was really strange was that this was the second time lighting had struck this year. About a month before I identified the quarter error, I was running some Mercury dimes through the coin counter at work when I culled out a 1945-D coin that at first glance seemed to have been cut down around the edge, as though to steal a bit of silver from the coin, but which upon closer examination appeared to have been struck that way.

A quick test of weight and specific gravity determined that the coin had been struck on a 2 gram, .750 fine silver planchet intended for a Philippines 10 Centavos coin, 137 million of which had been struck at the Denver Mint that year for use by the American liberators (including my father) of the islands. For comparison, a silver dime weighed 2.5 grams of .900 fine silver. The coin was well worn, and had obviously circulated unnoticed despite its smaller size and darker color until it had been pulled from circulation along with other silver coins in the 1960's. It is now in the hands of a local Philippines collector.

Error coins are commonly divided into three major categories depending upon whether the error involves the Planchet the coin was struck on, the Dies that struck it or the Striking of the coin itself. The initials of these three categories form an easy to remember acronym, P-D-S.

A very common planchet error is a lamination, in which the pure metals that make up the alloy are incompletely mixed and the coin develops cracks in it that may peel away in irregular layers. Modern clad coins infrequently split apart where one of the copper-nickel layers is bonded to the copper core, either before or after the strike. If before, the struck side of the core will be relatively smooth and normal; if after, the surface will be fairly rough and the image of the design on the missing layer will show through as a "ghost" image on the core.

Another common error is a clip, or incomplete planchet, which usually occurs when the circular planchet cutter (not unlike a cookie cutter) punches a blank out of a strip of metal and partially overlaps an earlier hole. The curved clip (or clips) that results is shaped somewhat like an elongated football; straight clips from the edge or end of a strip and irregular clips from broken or roughly cut strip ends and edges are also possible.

Wrong planchet errors such as those described above are usually the result of a planchet sticking inside a metal hopper used to transport first one denomination blank and then another inside the Mint. Years ago, while on a floor tour of the Denver Mint as an instructor with the ANA's Summer Seminar, I drifted away from our guide long enough to peer down into a row of empty hoppers lined up against a wall.

The fourth one I looked in had a five cents planchet caught between the bottom of the hopper and the trap door used to empty the hopper after it has been hoisted up above the feeding mechanism of a coin press. If that hopper were next used to transport quarter blanks without being checked first, the nickel blank would almost certainly end up being struck as a quarter.

The most common Die error is a die crack, whereby the steel die fractures wide enough for some of the coinage metal to flow up into the die and leave an irregular, raised line on the surface of the coin. Purists correctly insist that the crack was in the die, and not on the coin, but common usage calls the raised line on the coin the "die crack." Die cracks can be very helpful in identifying individual die varieties on 18th and 19th Century coins that are otherwise very similar.

If the crack in the die grows large enough, a piece of the die may break away and leave a void. Subsequently, when planchets are struck from this broken die, the metal in the planchet will take the path of least resistance, and tend to flow into the large void in the one die and not into the many small recesses in the opposing die. This will leave a raised, blank area on one side commonly called a "cud," and a weak or blank area on the opposite side of the coin.

A formerly common die error was the clashed die, whereby two dies came together without a planchet between them to absorb the blow, and part of the design of one or both dies was transferred to the opposing die. If this includes part of the lettering, it will appear both reversed and sunken on the coins struck from that die or dies. The markings that result are called clash marks. This type of error is less common on modern coins due to the addition over recent years of equipment on coin presses which automatically stops the press if a blank is not in position in the press for a strike, but it still is possible.

The popular 1937-D Three-Legged Buffalo nickel occurred when a pair of dies clashed and were heavily polished down to remove the clash marks. So much metal was removed from the die that one of the legs was also removed. Many other interesting die polish effects have occurred over the years, but few of them have any added value. This one does because there is a space for it in the more expensive coin albums.

A rare type of die error is a wrong denomination die, such as the Philippines 1918 San Francisco Copper-Nickel 5 Centavos struck from a 5 Centavos obverse and a 20 Centavos reverse, and the 1928 Manila Silver 20 Centavos struck from a 20 Centavos obverse and a 5 Centavos reverse. This type of error is usually possible only when the dies for the two denominations are approximately the same size, and more likely to occur if the designs are similar as the 5 and 20 Centavos dies are.

However, years ago I was able to correctly identify for the first time some mysterious clash marks on the obverse of an 1857 Flying Eagle cent as having come from the obverse die of a Seated Liberty half dollar! Although no piece is known today that was actually struck between two such dies, the night watchman at the Mint back then is known to have produced some other curiosities (such as 1804 Silver Dollars!) for sale to local collectors. Since I identified this piece, others have identified 1857 F.E. cents with clash marks on the reverse from the reverse die of a Seated Liberty Quarter, the corresponding 1857 Quarter with clash marks on the reverse from a F.E. cent reverse, and an 1857 F.E. cent with clash marks on the obverse from a Liberty Head $20 gold piece obverse!

Another type of die error I first identified was the misplaced date, usually found in the denticles below the date of various cents through double eagles of the 1850's through the early 1900's, but occasionally up high such as in the neck of the Indian on the cent or Miss Liberty on a gold piece or in the drapery folds of the Seated Liberty figure.

Although some of these may have occurred when an engraver accidentally bumped a date punch against a heat-softened die at random, it is now believed that the Mint used a positioning jig when punching dates into freshly hubbed dies, whereby the die was fixed into a clamp and a steel plate with a slot in it appropriate for the date position of that particular design was placed over it. The engraver slid the business end of a (usually) four-digit date punch through the slot and hit the other end of the punch once or more with a mallet, after which the die was inspected and then hardened for use. Late in a calendar year a three-digit punch might be used, the last digit being added when it was finally decided when the die was needed.

However, if the wrong cover plate was used, or if a cover plate that had, say, a slot for a Dime when turned one way and a different slot for a Quarter when turned 180 degrees was turned the wrong way, the slot would be higher or lower than intended for the die underneath and the engraver could not see his error until after he was finished. Many such misplaced dates have been discovered to date, and more are still being found.

Early dies were engraved piecemeal, starting with the design punch and adding the stars, letters and numbers by hand, occasionally with interesting blunders such as upside-down letters that may or may not have been corrected and misspelled words that were then corrected by one letter being punched over another letter. Just a few years ago I discovered that a known Bust silver dollar had a previously unnoticed N of UNITED punched over an earlier I. Old dies were sometimes overdated to show the current year, although the Mint often used outdated dies without bothering to change the date.

By the 1830's the Mint progressed to the point that all of the design except for the date and mint mark was on a single punch, or hub, which could then be used to hub identical working dies over and over. Because it takes several impressions to completely "sink" the die, with the die being heat softened between impressions, design doubling can occur if the die is not positioned exactly the same under the hub for each impression.

The most popular doubled die is the 1955 Cent, again because the more expensive coin albums have a slot for it. Curiously, the 1955 doubled die cent was discovered in the Mint before it was released, but released anyway because the product of that die had already been mixed in with other production and the Mint felt it was not worth the time and effort to sort them out of the other coins.

Nowadays, because of the 1955 cent, the hubs have raised ridges outside the design area to facilitate the correct alignment of die and hub. The numerous 1972 doubled die errors that are known resulted when an overzealous Mint worker ground off these ridges to "speed up production."

Striking errors tend to be the most spectacular of errors, such as off center and/or multiple strikes, including strikes on previously struck coins of the same or different denominations. Sometimes a coin may flip over between strikes. Indented strikes may occur when a planchet has part of a coin or another planchet either above or below part of its surface during its strike.

A brockage error occurs when a coin is struck and it then sticks to either the upper or lower die in the press, and a new planchet is then struck between the stuck coin and the other die. The resulting coin will have one normal side and a sunken mirror image of that side on the other side. If the stuck coin remains stuck, it will quickly expand and leave distorted impressions in the brockage coins. Such pieces are usually called "capped die strikes."

Thousands of other striking errors are also possible. The reader is referred to "The Error Coin Encyclopedia" by Arnold Margolis for further reading on the subject, including how to tell genuine errors from false ones.

Originally published in COINage magazine in November, 1994 under the title "Rare Errors." Reprinted with permission. Copyright 2002 by Thomas K. DeLorey.