Clayton, T. "Guinea". En Coins of England and Great Britain: "It has been dealt with here as the term guinea originally referred to the place in Africa from which much of the metal was obtained, rather than as a denomination. Its value fluctuated from the original 20 shillings, and it was not fixed at 21 shillings until late in 1717".
Clayton, T. "The Change to Decimal Coinage". En Coins of England and Great Britain: "The term guinea was (and is) used for 21 shillings (£1.05), especially in horse racing and by auction houses, although no coin of that value has been issued since 1813".
Margolin, S. (2010). "Guineas". En Rice, K. S.; Katz-Hyman, M. B. (eds.). World of a Slave: Encyclopedia of the Material Life of Slaves in the United States. ABC-CLIO. Páxina 259. ISBN 9780313349430. "The coins were named because much of the gold used to produce them came from the Gold or 'Guinea' Coast of West Africa and was provided by the Royal African Company, which had been granted a monopoly of the Africa trade from 1672 until 1698. Coins produced from African gold bore the company's distinctive emblem below the monarch's head: an elephant or elephant and a castellated howdah, an ornate canopied seat used for riding on elephants and camels".
