The design of the fifth Seal of George III can probably be attributed to the aging Nathaniel Marchant although, given the poor state of his health, he may have received some assistance. Marchant spent many years in Rome and was renowned for his reproductions of ancient statues and sculptures. Later in his career he became an engraver at the Royal Mint, his major contribution to numismatic design being the portrait of George III used on the gold coinage from 1804 to 1813.

The equestrian rather than the enthroned portrait was given the position of prominence on the obverse of the Seal, a significant break with tradition which nevertheless became accepted practice for the rest of the century. In a further departure, a distant view of Windsor Castle appears beneath the body of the horse instead of London and the River Thames.

On the reverse the King is seated on a gothic throne, with Minerva,Hercules and Justice to the left and Britannia and Religion to the right. A palm branch and rudder are placed in the exergue, intended to denote Britain's commercial strength and naval superiority. The Union Flag appears on the Seal for the first time, the cross of St Patrick having been added to those of St George and St Andrew on 's shield.