Isaac Newton, the Master of the Mint, wrote a minute dated 21 September 1717 in which he blamed the rising price of silver on the overvaluation of the guinea at twenty-one shillings and sixpence.

Newton's memo resulted in a Proclamation of 20 December reducing the value of the guinea to twenty-one shillings.

The obverse shows a right-facing portrait of the king with the legend GEORGIVS D G M BR FR ET HIB REX F D, abbreviation for Georgius, Dei Gratia Magna Britannia, Francia, et Hibernia Rex, Fidei Defensor, which is Latin for "George, by the Grace of God King of Great Britain, France and Ireland, Defender of the Faith".

The reverse shows four crowned cruciform shields separated by sceptres, with a central Star of the Order of the Garter, and the legend BRVN ET L DVX S R I A TH ET PR EL 1718 – Brunswick et Luneburg Dux, Sacrum Romanum Imperatoria Arch-Tresorum et Princeps-Elector, Latin for "Duke of Brunswick and Lüneburg, Arch-Treasurer and Prince Elector of the Holy Roman Empire".

The obverse shows a right-facing portrait of the king with the legend GEORGIVS III DEI GRATIA, while the reverse shows a large crowned shield bearing the arms of England and Scotland, France, Ireland, and Hanover, and the legend M B F ET H REX F D B ET L D S R I A T ET E 1762 – abbreviation for Magna Britannia, Francia, et Hibernia Rex, Fidei Defensor, Brunswick et Luneburg Dux, Sacrum Romanum Imperatoria Arch-Tresorum et Elector - Latin for "King of Great Britain, France, and Ireland; Defender of the Faith, Duke of Brunswick and Lüneburg, [and] Arch-Treasurer and Elector of the Holy Roman Empire".