Glossary of Numismatics - K

K

Karat

Unit measurement of the purity of gold. Usually marked 'K', or 'k'. 24K = pure gold, 18K = .750 fine. Not to be confused with 'Carat' used with precious stones. Note that both originally referred to the seed of the carob tree ('Ceratonia siliqua' or 'Siliqua Graeca'). A Roman coin called the solidus weighed 24 'carats' or 'siliquae', 1/6 of a scruple; this became the standard in purity in western Europe.

Key Coin

A rarer or higher valued coin within a series. As an example, 1923 and 1925 are key coins in the Canadian small cent series.