Industry WIKI

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.

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