Usually a grade is applied to indicate the condition of a coin. The condition that the coin is in is of extreme importance, as condition follows rarity and demand in determining a coin's value. As a rule, the higher the grade of a coin, the more valuable the coin will be. Because there are naturally some variations within this general rule, coin collectors have developed a variety of methods and systems for describing a coin's general condition.
There are various things that influence the grade of a coin. The factors that go into determining the grade of a coin are luster, surface condition, eye appeal, and strike. Without all of these qualities present, the value and grade of the coin will be reduced. Sometimes the quality differences among coins are so minor as to be unnoticeable to the untrained eye. In this case, an expert must be called in to grade the coin. Sometimes an expert grader will give the same coin two different grades and leave the final decision as a matter of opinion.
If you follow a few simple guidelines, you can learn to grade coins with fair accuracy, even as a beginner. Of course, to do so consistently and with an exacting accuracy requires a great deal of experience and talent. When assigning a grade to a coin, the Zero-Seventy point numeric system developed by the American Numismatic Association is often used.
The best grade a coin can be given is uncirculated, or mint state. The lowest grade that can be given to a proof or uncirculated coin is 60. A coin without wear that shows some contact marks, has spots on the surface, or lacks luster will receive a grade of 60. If you have a coin that has no evidence of contact with other coins or handling, shows no trace of wear, has no scratches, and is in perfectly new condition, it is termed an uncirculated coin and will receive a grade of 70.
Another very high quality coin grade is "proof". This term refers to the way a coin is manufactured. It does not refer to the coin's condition. It's a specially crafted coin distinguished by the sharpness of the coin's detail; it most often has a shiny mirror-like surface.
A coin that has a little trace wear on its highest design points and has no other defects is referred to as Choice About Uncirculated or AU-55. It is important to note that coins that are thus described will also have retained most of their original luster. You will find trace wear on the highest areas of an AU-55 (About Uncirculated) coin. This coin should retain at least half of the original luster imparted at the mint. A coin that has noticeable wear but still has sharp features is termed Extremely Fine, EF-40. Here are the grades of coins in descending order: Very Fine, Fine, Very Good, and Good to About Good.
The value and grade of a coin is dramatically reduced by damage. Some examples of damage are: gouges, holes, re-engraving, edge dents, cleaning, and repairs. Some dishonest collectors will polish or clean coins and try to trick unsuspecting collectors into thinking that they are of high grade or uncirculated quality. Coins that have been cleaned can have a lower value and grade.
When the condition of two sides of a coin differ greatly, a grade that is split may be assigned. A "/" in the grade indicates a split grade. If one side of a coin is considered "AU" and the other side is considered "EF", it will receive a grade of "AU/EF".