The guinea is a coin that was minted in the Kingdom of England and later in the Kingdom of Great Britain and the United Kingdom between 1663 and 1813. It was the first English machine-struck gold coin, originally worth one English Pound sterling, equal to twenty shillings; but rises in the price of gold caused the value of the guinea to increase, at times to as high as thirty shillings; from 1717 onwards its value was officially fixed at twenty-one shillings, after Great Britain adopted the gold standard.