The year 1797 saw the introduction of which unit of currency?

The guinea was officially introduced as a unit of currency in 1797 in Great Britain, though it had been used unofficially since 1663. Named after the West African region where gold was sourced, it was worth 21 shillings and was used in luxury transactions and professional fees. The shilling and crown were much older, and the one pound note came later. The guinea remained in use until 1817.