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Mint State
The Sheldon Coin Grading Scale is a 70-point coin grading scale used in the numismatic assessment of a coin's quality. The American Numismatic Association based its ''Official ANA Grading Standards'' in large part on the Sheldon scale. The scale was created by William Herbert Sheldon. Original Sheldon Scale (1949) In 1949, the original scale was first presented in "Dr. William H. Sheldon's Early American Cents" titled "A Quantitative Scale for condition" as a way to grade Large cents. The scale is known today as the Sheldon scale. Adapted scale (1970s–present) By 1953 the original Sheldon scale had become outdated. It was not until the 1970s, however, that the ANA chose to adapt the scale for use on all US coins. The scale used today is a modification of the original Sheldon scale, with added adjustments, additions, deletions, and modifications to it. ''Note'': Some early American coin varieties are almost always found to be weakly struck in places. This does not bring t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, aluminum, magnesium, neodymium and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish, although it may tarnish with oxygen over time. It often appears as a dull, gray or black film or coating over metal. Tarnish is a surface phenomenon that is self-limiting, unlike rust. Only the top few layers of the metal react, and the layer of tarnish seals protects the underlying layers from reacting. Tarnish actually preserves the underlying metal in outdoor use, and in this form is called patina. The formation of patina is necessary in applications such as copper roofing, and outdoor copper, bronze, and brass statues and fittings. Patina is the name given to tarnish on copper-based metals, while toning is a term for the type of tarnish which forms on coins. Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen, hydrogen or hydroxide. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases. Many structural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleaning (coinage)
Coin cleaning is the process of removing undesirable substances from a coin's surface in order to make it more attractive to potential buyers. The subject is disputed among the numismatic community whether cleaning coins is necessary. Those that argue in favor of cleaning are also in dispute on which methods work best. It was once common practice to clean coins as the method was recommended by experts in the field. Solutions from pencil erasers to wire brushes and potassium cyanide were all used as cleaning agents with the goal to make the coin look brilliant again. When certified grading came into use in the mid 1980s though, the practice of cleaning coins diminished over time. Most coin experts have since come out against cleaning coins, as doing so can negatively affect them both in grade and value. If a potentially valuable coin must be cleaned (for example if the coin is deformed) then professional work is recommended. Commonly found coins are mentioned as ideal candidates for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...—its atom making four electrons available to form covalent bond, covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three Isotopes of carbon, isotopes occur naturally, Carbon-12, C and Carbon-13, C being stable, while Carbon-14, C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the Timeline of chemical element discoveries#Ancient discoveries, few elements known since antiquity. Carbon is the 15th Abundance of elements in Earth's crust, most abundant element in the Earth's crust, and the Abundance of the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature. Sulfur is the tenth most abundant element by mass in the universe and the fifth most on Earth. Though sometimes found in pure, native form, sulfur on Earth usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, and ancient Egypt. Historically and in literature sulfur is also called brimstone, which means "burning stone". Today, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas and petroleum.. Downloahere The greatest commercial use of the element is the production o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Numismatic Guaranty Company
Numismatic Guaranty Company (NGC) is an international third-party coin grading and certification service based in Sarasota, Florida. It has certified more than 50 million coins. NGC certification consists of authentication, grading, attribution, and encapsulation in clear plastic holders. NGC is a subsidiary of Certified Collectibles Group (CCG), which owns six collectible certification services and is in turn owned by Blackstone, a multibillion dollar New York City hedge fund. History NGC was founded in 1987 in Parsippany, N.J. as one of the first independent third-party coin grading companies. In 1995, NGC was named the official grading service of the ANA, though this is purely for marketing purposes as the ANA does not encapsulate coins in its collection, and those that are encapsulated are a mix of donated coins by different services including rivals such as PCGS. NGC commenced operations at its new location in Sarasota, Florida in 2002. That same year, NGC was named the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toning (coin)
Toning on a coin is the change of colour brought about through oxidization, which forms a thin layer of tarnish on the metal's surface. Coin toning can vary in aesthetics, and thus can alternately add or detract from a coin's value. Coins with unusual toning colours or patterns tend to be valued by coin collectors. Toning is most common on silver coins, but can be found on coins minted from other metals and alloys, including gold, copper and cupronickel. Types of toning Different colors and patterns of toning can have varying effects on a coin's grade and value. For example, brown spotty toning could decrease a coin's value, while colorful rainbow toning could increase it. Similarly, toning can raise or lower a coin's grade by several points, as grading is based on factors including eye appeal and not just wear. Depending on the environment in which the toning took place, toned coins can come in many different colors and color combinations. Toning patterns may cover an entire co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mint-made Errors
Mint-made errors are errors during the mint (coin), minting process. Groups of coins with distinctive characteristics are known as varieties. The term variety applies to coins with both intended and unintended differences while the term error refers only to coins with unintended differences. Nevertheless, not all errors are varieties. Although there may be many identical examples of some errors, others are unique. For example, there may be many indistinguishable examples of coins with a specific die crack, while off-center strikes tend to be unique. Being unique does not mean that an error is valuable. Although no other coin may be similar to a coin with an off-center strike, off-center strikes happen often enough that buyers can choose from many examples each of which varies slightly from the other. Mint error coins can be the result of deterioration of the minting equipment, accidents or malfunctions during the minting process, or intentional interventions by mint personnel. Acc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planchet
A planchet is a round metal disk that is ready to be struck as a coin. An older word for planchet is flan. They are also referred to as blanks. History The preparation of the flan or planchet has varied over the years. In ancient times, the flan was heated before striking because the metal that the coin dies were made of was not as hard as dies today, and the dies would have worn faster and broken sooner had the flan not been heated to a high temperature to soften it. An unusual method was used to mint the one-sided, bowl-shaped ''pfennigs'' of the Holy Roman Empire. The planchet used for these so-called ''Schüsselpfennigs'' was larger than the coin die itself. The coins were made by striking with only one upper die on the larger planchet. As a result, the perimeter of the planchet was pressed upwards in the shape of a bowl or plate. Until the 18th century they were minted mainly in the Harz Mountains. The curved shape of the pfennig was very useful for handling small change ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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