How much was a guinea worth in the British pre-decimal currency?

The guinea was a coin of approximately one quarter ounce of gold that was minted in Great Britain between 1663 and 1814. 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. Then, Britain adopted the gold standard and guinea became a colloquial or specialised term.

The gold guinea was undoubtedly the major British coin of the eighteenth century. It was born in the aftermath of the English Civil War when the republican issues were replaced with a more impressive coinage bearing the portrait of the newly restored King, Charles II. Romantically named ‘guinea’ since gold for coining was then supplied by the Africa Company operating along the Guinea Coast, it was given a nominal value of 20 shillings. Its actual value fluctuated until finally stabilising, in 1717, at 21 shillings, a monetary unit used up decimalisation in 1971.

Although no longer circulated, the term guinea survives in some circles, notably 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 in decimalised currency.