George III was king of Great Britain and Ireland until January 1, 1801 when the union of the two Kingdoms was officially marked. This fantastic piece was struck in c. 1811 which was a time when the king had suffered a mental relapse. George III suffered off and on from mental illness and the final relapse in 1810 brought his son, his regent, into power. 

George was involved in some historical altering battles such as the Seven Years War with France which occurred from 1756-1763. This dictated sovereignty over places like North America and India. George was also in power during the Napoleonic Wars which culminated at the Battle of Waterloo and the defeat of Napoleon.

Likely the most notorious battle George III is associated with is the American War of Independence in 1775-1783 which ended in the thirteen colonies becoming independent from Great Britain and their King, George III.