I am fairly new to Ancient Coin collecting and want to pass on what I learn to others that may also be new to Ancient Coins. Here is what I have learned about Ancient Coin grades.
Describing and grading a coin is very subjective. For those that collect modern U.S. Coins, you are most likely used to the Sheldon Grading Scale 1 - 70. The Sheldon Grading Scale is a 70-point scale for grading coins, developed by Dr. William Sheldon in 1949. For Ancient Coins it is a whole new world of grading, but, here is what you can expect to see when dealing with Ancient Coin grades.
FDC. Fleur de Coin, literally "flower of the die." This implies perfection of strike with an absence of wear. The equivalent on the Sheldon Scale would be MS-68 to MS-70.
Mint State. Without any wear whatsoever. The coin could be double struck, of poor style, or a gem. These other factors must be listed.
Superb. Implies an example of beauty and little or no wear. This grade, like FDC, combines the absence of wear with a special quality and no imperfections.
(These three grades above are extremely rare and are almost never given).
Most of the Ancient Coin Grades will be the following:
Extremely Fine (EF). Again, little or no wear; the highest points of the coin might show an indistinctness or be very slightly rubbed. This is normally as high a condition as one can aspire to in ancient coinage.
Very Fine (VF). Even wear with nice definition. A handsome coin to be proud of, in which the sharpness of an EF coin has been lost through gentle circulation. This grade encompasses split or "in-between" grading:
Choice VF. Implies a really handsome coin with VF grade wear.
VF+. Less wear than normal on a VF coin.
VF-EF. In terms of detail and wear, some aspects of VF and some of EF.
VF/EF. Very Fine obverse coupled with an Extremely Fine reverse.
About VF. Close to being a Very Fine coin in terms of circulation.
Fine (F). The relief of the coin has now been noticeably lessened, with further loss of detail; inscriptions are worn.
Very Good (VG). More wear than Fine, often losing all hair details in portraits.
Good (G). Normally the lowest condition for clear inscriptions and respectable types.
Fair, Poor, and Mediocre. Can be used to describe excessively worn, low-grade specimens.
Source: Collecting Ancient Greek Coins - A Guided Tour Featuring 25 Significant Types by Paul Rynearson. 2009 Whitman Publishing, LLC.