Definitions

This post gives some of the common terms used in the coin collecting hobby and its meaning.

Abrasions	Light marks of scuffing or rubbing typically from friction
Alloy	A combination of more than 1 metal. Most coins are made of Alloy for cost and making it difficult for melting. i.e. A coin of Alloy would cost more segregate the metals after melting
Annealing:	The process of heating & cooling the coin blanks (planchlets) in a furnace to soften the metal prior to them being struck.
Anvil Die:	See Die, Anvil
AUNC:	[Almost UNC]. Term used by small time dealers to pass of a used coin as UNC.
Bag mark	Typically coins are put into a Bag, and one coin comes in contact with others, often leaving a mark.
Blank:	A piece of metal of right shape that is punched out of the sheet of metal. This blank when treated goes on to become Planchet on which coins are then stuck.
Bottom Die:	See Die, Anvil
Bronze	An alloy of Copper, Zinc and Tin. A popular combination for minting coins. The exact composition of the Copper, Zinc and Tin is decided on need basis.
BU:	See BUNC
BUNC :	[Brilliant Uncirculated] a descriptive term used to indicate an uncirculated coin that still retains a lot of the brilliant luster. Not a heavily toned coin. BU is used to abbreviate brilliant uncirculated. The term is often used with Silver Coins, as Silver coins even if UNC can have toning.
Business Strike:	See Strike, Circulation
Cameo Finish	Similar to Mirror Finish however the dies further treated to nitric acid and alcohol to produce a light frosting over the entire die surface. This frosting is called Cameo effect. The surrounding areas would be polished to have a mirror finish on the background leaving the main design
Cameo:	A coin (usually a proof) that has a mirror like background to the surface of the coin and a design that is frosted looking. Special treatments of the dies make this cameo frosted effect. In older minting process, the initial coins stuck when the die was new might have a cameo appearance. Later as the dies starts to wear (or break in) the coins produced will have less and less of the cameo frosting.
Circulation Strike:	See Strike, Circulation
Cleaning	A process of removing the dirt or changing the coin to look good. The term cleaning is used in –ve context. Typically this process is used to make the coin look good. Also see preserving.
COA:	[Certificate of Authenticity]. A paper certificate usually from the issuing mint that declares the coin or item is genuine, typically also gives of the details of weight and composition in Indian Proof and UNC Sets.
Commemorative Coins	A coin issued to celebrate a specific event or mark a special occasion.
Cud:	A type of error when a coin is struck by a broken die[Minor Die Break] the place where the die is broken will show extra metal [or flat and not stuck part] on the surface of a coin. This area of the coin is called "Cud".
DDO	Double Die Obverse in which the doubled images in one or more places on the Obverse die. Also see DDR
DDR	Double Die Reverse in which the doubled images in one or more places on the Reverse die. Also see DDO
Definitive Coins	Coins used for normal every day usage. a.k.a Standard Coins
Designer	The artist who creates the coins design
Details	Small features of the coin. i.e. one would say this coin has rich features and good details.
Die, Anvil:	A coin is struck using 2 dies. One for the Obverse and one for the Reverse. The Anvil Die is the one which is placed at the bottom and also called “Bottom Die”. The origin of the term lies in the fact that in older times, the Die was placed on an Anvil, the coin blank [planchet] placed on top of this die and other die placed on top. This was then struck with an Hammer. The die placed on the bottom was hence called Anvil Die. As a convention the Reverse die is placed on the Anvil. The wear on the Anvil die is less than that of the Hammer die.
Die, Hammer:	A coin is struck using 2 dies. One for the Obverse and one for the Reverse. The Hammer Die is the one which is placed at the top and also called “Top Die”. The origin of the term lies in the fact that in older times, the Die was placed on an Anvil, the coin blank [planchet] placed on top of this die and other die placed on top. This was then struck with an Hammer. The die placed on the top was hence called Hammer Die. As a convention the Obverse die is placed on the Hammer side. The wear on the Hammer die is more than the Anvil die.
Die:	A metal object that has the impression in incuse [negative], so that when struck the image in relief[positive] gets created on the coin blank.
Edge, Milled:	The edge that has series of lines engraved on it.
Edge, Plain:	The edge that has no special design and is plain.
Edge, Reeded:	The edge that has series of lines engraved on it. Same as Milled.
Edge, Security:	The edge apart from the lines engraved on it has a pattern engraved to make counterfeit difficult.
Edge:	The periphery or the border side of the coin. Also referred to as 3rd side.
Engraver	A person who creates the Master die from the design
Hammer Die:	See Die, Hammer.
Head:	See Obverse.
Incuse	The design of the coin that is below the coins surface. All Master Die and working Die’s will be in Incuse so that when struck the coins will have relief. The Brockrage [Lakhi] coins show incuse.
Legend	The main inscription around the outer periphery of the coin. Typically more pronounced in the Commemorative issues.
Luster	The Glossy appearance of the surface of the coin. This is typically brilliant when freshly minted. Over period the surface looses luster and may become dull, frosty, spotted or discolored.
Matte Finish	Similar to Mirror Finish, however a rough granular feature is obtained by sandblasting
Milled Edge	See Edge, Milled
Mint Mark	A symbol or a letter adopted by the Mint to identify / indicate the mint from where the coins were minted / struck.
Mint Mark, Diamond	The Mint Mark used by Bombay / Mumbai Mint in the shape of small Diamond
Mint Mark, Dot in Diamond	The Mint Mark used by Hyderabad Mint where the Diamond has a small dot [incuse] in the center to distinguish it from Mumbai Mint mark
Mint Mark, Split Diamond	The Mint Mark used by Hyderabad Mint where the Diamond was split in center
Mint Mark, Star	The current mint mark adopted by Hyderabad Mint in the shape of Star
Mirror Finish	The dies are cleaned and polished with diamond paste to create a mirror like finish on the coins that are struck. Normally used to strike proof coins.
Mule	A coin struck with pair of Obverse and Reverse that were not intended to be used together. Indian has quite a few interesting Mules.
Mylar:	A trademark polyester material used to store coins. PVC spoils the coins and corrodes them. Mylar is neutral and does not spoil the coin.
Numismatics	Study relating to coins
Numismatist	A coin collector or student or expert
Obverse:	Also called Head. The most significant side of the coin. In Indian coinage this is the side that have Value imprinted. It is quite confusing in Indian coinage as we have “Ashoka Emblem” on one side of the coin and this resembles “Head” to most common people. Hence if you are tossing a coin, define the Head and Tail before hand. In most Indian Coinage, the side having the Ashoka Lion is actually Tail or Reverse.
Off Center:	A type of error coin in which the details are not centered but as off, the coin shows partial blank face and partial image of the indented strike.
OMS:	Off Metal Strike, a type of error where the metal used for minting is different from the one intended for minting the particular denomination coin. This type of error happens at the first stage of planchet creation.
Patina	A green or brown flim on ancient copper or bronze coins caused by Oxidation.
Pattern	A prototype of the proposed coin design.
Plain Edge	See Edge, Plain
Planchet:	A blank round [or of the right shape] piece of metal that is ready to be stuck so as to create a coin. This is also called flan
Preserving	This is used in the +ve Context. A process adopted to prevent the coin from further damage. i.e. remove dirt or any acid or any other material that if left as is would damage the coin further. Also see Cleaning.
Proof Coin:	See Strike, Proof
Proof Strike:	See Strike, Proof
Reeded Edge	See Edge, Reeded
Relief:	The part of the design that is raised from the surface of the coin. If the design is above the coins surface its said to be in relief. Normal coins that one see, even the Hub’s [used to make the Master / working dies] would have relief
Restrike:	A coin minted from original set of dies by the mint at a later date for a second time.
Reverse:	Also called Tail. The side opposite to Obverse. In Indian coinage, this varies, in most definitive’s it can be said to be the side with “Ashoka Emblem” but not always, in commemorative coins, it’s the side with commemorative theme.
Rim	The raised portion of the coin in circular shape on the periphery on both Obverse and Reverse side. This has multiple purposes like preventing the metal to flow over during coin strikes, to have the ability to stack coins, prevent wear on the coins
Rim:	The raised position on both sides of the coin around periphery. The Rim helps stop the metal flow with the coin is struck. It also helps stack the coins on top of each other. The Rim also prevents / reduce the wear on the coin in normal course of usage.
Security Edge	See Edge, Security
Standard Coins	See Definitive Coins
Strike / Strikes:	Defines how the coins were struck. There are different types of strikes with respect to Indian Coinage.
Strike, Circulation:	Also called Business Strike. Most common strike for circulating coins. The details are not sharp. They are stuck using high capacity machines often striking nearly 40 coins per second or even faster.
Strike, Proof:	A coin that is struck as proof means its at least struck 2 or more times. There is mirror and or frost finish. The details are very sharp and clear. The dies themselves have quite a good incuse so that coin details come out good. The dies are specially polished and coins are hand struck and inspected. In case the number of coins being struck is large, the dies are polished again after every few strikes. These are the best grade of coins. The are specially packaged for collectors and sold at premium by Mint. Proof Coins are typically sold from mint in the year of release by inviting bookings. The mintage is to the order of bookings.
Strike, UNC:	In Indian coinage, the Indian Mints also strike some called UNC Strike. These are similar to Proof strikes in quality, however the dies are not sand blasted to have frost finish. The quality of strike is quite good. These are again specially packaged for collectors and sold at premium by Mint. The premium is slightly less than that of Proof.
Tail:	See Reverse
Toning	The natural discoloration of the coin, typically silver by coming in contact with the atmosphere over a long period of time. Toning is considered attractive and quite a few collectors would prefer coins with toning.
Top Die:	See Die, Hammer.
UNC Strike:	See Strike, UNC
UNC:	Uncirculated coins. These are in mint condition and have not been used / handled. Typically an ardent collector will want to have all his collection in UNC
Upsetting Mill:	A machine used to produce the Rim on both sides of a Planchet.
Variety	A minor change to the basic design of the Die.