[The following excerpt is published courtesy of DLRC Press and its author, John Feigenbaum. This information was originally published in 1994 in The Complete Guide to Washington Quarters.]

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ALTERED COIN – A genuine coin that has been deliberately changed, usually to make it resemble a rare or more valuable piece.  For example, by the addition or removal of a mintmark.
ANACS – A coin authentication and grading service located in Columbus, Ohio.
ATTRIBUTION – The identification of a numismatic item by characteristics such as issuing authority, date or period, mint, denomination, metal in which struck and by a standard reference.
BUSINESS STRIKE – A coin which was minted for public circulation.  As opposed to a proof.
CHERRYPICKING – The art of searching through a group of coins offered for sale and finding a variety of some value over and above the selling price.
CIRCULATED – Coins showing signs of wear through use in commerce.
COIN DEALER NEWSLETTER (CDN) – A publication reporting current wholesale market values.  Published in Torrence, California.
COUNTERFEIT COIN – A coin made outside of the U.S. Mint to imitate a genuine piece with intent to deceive or defraud, irrespective of whether the intended fraud is for monetary or numismatic purposes.
D MINT – Denver Mint.
DDO – Doubled Die Obverse.
DDR – Doubled Die Reverse.
DIE – The metal molds which stamp a design into a blank planchet so the devices and inscriptions will be in relief and readable.  The die design is incuse.
DIE CRACK – A raised, usually irregular line on the coin resulting from a crack in one of the dies.
DOUBLED DIE – One which received one of its several blows from a hub or device accidentally punched in imperfect alignment.
FILLED DIE – Results when dirt or grease pack into the letters or numbers preventing the coin metal from entering that part of the design in the dies as the coin is struck.
FLOW LINES – Microscopic striations in a coin’s surface caused by the movement of metal under striking pressures.
FROST – Effect caused by striking a coin with sandblasted dies, used in describing some uncirculated and mostly proof coins.
HAIRLINES – Fine scratches in the surface of a coin caused by mishandling or light cleaning.  Not to be confused with die scratches or die striations which are raised on the coin.
LUSTER – The sheen or bloom on the surface of an uncirculated numismatic object resulting from the flow of metal caused when struck by the dies.
MASTER DIE - The die made from the master hub in which the year is engraved and used to produce the working hub.  The working hubs are then used to produce the working dies utilized by the mint presses.
MINT ERRORS – A coin evidencing a mistake made in its manufacturer at the mint.
MINTMARK – Letter or symbol identifying the mint of origin of a coin.  The mint marks are normally punched by hand into each working die at the Philadelphia Mint.
NGC – Numismatic Guaranty Corporation of America. A coin certification and grading service located in Parsippany, New Jersey.
OBVERSE – The “heads” side of a coin.  The side with the date.
OVERDATE- A variety in which at least one digit of a date has been changed either for mint economy or to correct a blunder. Some part of the earlier date still shows.
P MINT – Philadelphia  Mint.
PCGS – Professional Coin Grading Service.  An independent certification and grading service located in Newport Beach, California.
PLANCHET – The blank disc of metal on which the dies of the coins are impressed to make the coin. Also called a blank or disc.
PROOF – Specially minted coin, normally given two or more blows from the dies to bring up the designs more sharply than on production coins.  Usually minted on burnished blanks from burnished dies giving the coins a mirror finish.
RED BOOK – “A GUIDE BOOK OF THE UNITED STATES COINS” by R.S. Yeoman, published by Western Publishing Company, Inc., of Racine, Wisconsin.  A retail price guide.
REVERSE – The “tails” side of a coin.  In this series, the side with the eagle.
RPM – Repunched Mintmark.  The mintmark has been punched into the die twice resulting in a doubled mintmark on the coin.  Since the doubling appears on the die itself, identical specimens are produced and the variety is considered collectable.
S MINT – San Francisco Mint.
SLAB – A coin encased in hard plastic by one of the certification services.  After grading, the enclosed coins receive protection from the outside environment.  The holders are tamper resistant.
SLIDER – Current slang for a coin that is close to uncirculated (AU58) and possibly saleable as mint state, particularly after cleaning and/or recoloring.
STRIKE -The quality of the coin’s detail transferred from the dies.  Poor strikes can be caused by light striking pressure, worn dies or improper distant adjustments between the obverse and reverse dies.
WHIZZING – The severe polishing or buffing of a coin in an attempt to improve its appearance and salability to the uninformed.  A form of alteration regarded as misleading by the numismatic community and which actually lowers the value of the coin significantly.
VARIETY – Any coin which is recognizably different from another of the same design, type, date and mint due to a difference in the die which produced it.