The Spanish dollar, also known as the piece of eight, is a silver coin of approximately 38 mm (1.5 in) diameter worth eight Spanish reales. It was minted in the Spanish Empire following a monetary reform in 1497 with content 25.563 g (0.8219 ozt) fine silver. It was widely used as the first international currency because of its uniformity in standard and milling characteristics. Some countries countermarked the Spanish dollar so it could be used as their local currency.

The real was a unit of currency in Spain for several centuries after the mid-14th century. It underwent several changes in value relative to other units throughout its lifetime until it was replaced by the peseta in 1868. The most common denomination for the currency was the silver eight-real Spanish dollar or peso which was used throughout Europe, America and Asia during the height of the Spanish Empire.