Industry WIKI

Coin cleaning is the controversial process of removing undesirable substances from a coin's surface in order to make it more attractive to potential buyers. Coin cleaning is not advised as it generally decreases its value by removing the coin's patina, the surface valued by collectors. Whether cleaning coins is necessary is a subject disputed among the numismatic community. Those that ar

Proof coinage refers to special early samples of a coin issue, historically made for checking the dies (as in demonstrating that something is true) and for archival purposes. In modern times, proofs are often struck in greater numbers, especially for coin collectors (numismatists). Nearly all countries have issued proof coinage.

The Standard Catalog of World Coins is a series of numismatic catalogs, commonly known as the Krause catalogs. They are published by Krause Publications, a division of Active Interest Media.

The Standard Catalog of World Paper Money was a well-known catalogue of banknotes that was published by Krause Publications in three volumes. These catalogues are commonly known in the numismatic trade as the Pick catalogues, as the numbering system was originally compiled by Albert Pick, but are also referred to as "Krause" or "SCWPM". Since the mid-1980s the titles have been owned by K

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, typically as a result of interactions and chemical reactions with sulfur-containing compounds in the environment. Coin toning can vary in aesthetics, and thus can alternately add or detract from a coin's value. Coins with unusual toning colours or patter