King William III of England took power in the "Glorious Revolution" after defeating the forces of James II of England at the Battle of the Boyne in 1690. This began the reign of William and Queen Mary (also his cousin). William was previously, and also, William of Orange, basically the boss of the Republic of the Netherlands. So the Dutch conquered England and installed their own monarchy. King William III ruled until his death in 1702, one year after this coin was struck.
King William III was famously implicated in the privateer contract with Captain William Kidd who is considered by many to have been a pirate. My understanding from the contemporary records cited in the great book "Pirate Hunter" is that Captain Kidd did everything he could to honor the terms of his privateer contract with the King of England brokered by the Earl of Romney. But he wound up being hung as a pirate in England while the real pirate - Robert Culliford - disappeared with a fortune in gold and treasure stolen from a giant Muslim pilgrimage ship taken in the Red Sea.
There are only three of these in higher grades at NGC and PCGS together, with just 6 graded total.
Weight: 4.175gAGW: 0.1231ozDiameter: 21mm