Guinea (British currency unit)

The guinea was a coin of approximately one quarter ounce of gold that was minted in Great Britain between 1663 and 1814. The name came from the Guinea region in West Africa, where much of the gold used to make the coins originated. It was the first English machine-struck gold coin, originally worth one pound sterling, equal to twenty shillings, but rises in the price of gold relative to silver caused the value of the guinea to increase, at times to as high as thirty shillings. From 1717 to 1816, its value was officially fixed at twenty-one shillings.

When Britain adopted the gold standard the guinea became a colloquial or specialised term. Although no longer circulated, the term guinea survives as a unit of account in some fields. Notable usages include horse racing, and in the sale of rams to mean an amount of one pound and one shilling (21 shillings) or one pound and five pence (£1.05) in decimalised currency. The name also forms the basis for the Arabic word for the Egyptian pound الجنيه el-Genēh / el-Geni, as a sum of 100 qirsh (one pound) was worth approximately 21 shillings at the end of the 19th century.

The first guinea was produced on 6 February 1663; a proclamation of 27 March 1663 made the coins legal currency. One troy pound of 11/12 fine gold (22 carat or 0.9167 pure by weight) would make 44½ guineas, each thus theoretically weighing 129.438 grains (or 8.385 grams).

The denomination was originally worth one pound, or twenty shillings, but an increase in the price of gold during the reign of King Charles II led to the market trading it at a premium. The price of gold continued to increase, especially in times of trouble, and by the 1680s, the coin was worth 22 shillings. Indeed, in his diary entries for 13 June 1667, Samuel Pepys records that the price was 24 to 25 shillings.

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