Die: An engraved piece of metal used to stamp a design on a coin.

Die crack: A small, raised imperfection on a coin resulting from a crack in the stamping die.

Early release: The Numismatic Guaranty Corporation (NGC) uses this designation for U.S. Bullion Coins during the first month of release from the U.S. Mint. To qualify for Early Release designation, NGC must receive the coins within 30 days of their release by the US Mint or properly documented as being received by an NGC approved entity within the same 30-day release period.

Encapsulated coin: A coin graded and authenticated by a professional coin service, then sealed in plastic.

Field: The typically flat area surrounding the relief and not used for legend or inscription.

Legal tender: Official money issued by the government.

Legend: The coin's primary lettering.

Lettered edge: An inscription added to the edge of a coin.

Luster: The quality of the surface brilliance on a Mint State or Uncirculated coin.

Mercury dime: Issued from 1916 to 1945, this U.S. dime featured a representation of Liberty in a winged hat that was commonly mistaken for the ancient god, Mercury.

Mint: A government controlled coin production facility.

Mint mark: A small letter stamped on a coin that indicates its mint origin, ex. "D" for Denver.

Mint Set: One coin from each of the available denominations in a particular year, produced by a single mint and made for circulation.

Mint State (Uncirculated): A regular production coin never used in trade and existing in its original condition.

Mintage: The number of coins produced.

NGC: Numismatic Guaranty Corporation.

Numismatics: The collection and study of monetary objects such as coins and paper bills.

Obverse: Heads, or a coin's front side.

Patina: Surface discoloration, typically green or brown, caused by oxidation over time.

PCGS: Professional Coin Grading Service.

Planchet: A blank metal piece used to produce a coin.

Proof: Expertly polished planchets and dies produce these coins which feature an extremely high quality strike, resulting in unmatched detail and brilliant surface finish.

Reeded edge: A coin edge finish featuring parallel vertical grooves all the way around.

Relief: The raised portion of a stamped design that sits above the coin's field.

Reverse: Tails, or coin's back side.

Rim: The raised ring around the perimeter of a coin designed to reduce wear on the relief.

Strike: The act of stamping a coin.

Truncation: The bottom edge of a portrait or bust.

Wheat penny: Lincoln cents issued from 1909 to 1958 bearing the wheat ear design on the reverse.