The coinage of the Polish, Lithuanian and Silesian King and Prince Sigismund I (Old) from 1499 to 1548 was the result of the financial reforms carried out during his reign. The aim of the reforms was to stabilize the financial system, protect the value of the currency and boost trade. One of the important elements of the reforms was the transfer of the monopoly of coinage to the king. Before that, minting could be practiced by both cities and private individuals, which often led to counterfeiting and a decrease in the value of the currency. King Sigismund concentrated minting in his mint in the royal court and strictly controlled the quality of minting. The royal coat of arms was depicted on the obverse of the coins, and St. László on the reverse. Another important element of the reforms was the standardization of the weight and purity of the coins. King Sigismund introduced the Polish złoty, which consisted of 30 grosz. The gros was made of silver and weighed 2.06 grams. As a result of the reforms, the Polish monetary system became more stable and reliable. The złoty became one of the most valuable currencies used in Central Europe in the 16th century. King Sigismund's coinage was one of the most important periods in Polish monetary history. The reforms contributed to the development of the Polish economy and the flourishing of the Renaissance in Poland. King Sigismund's coinage included the following denominations: gold forint (ducat), silver forint (zloty), grosz, half grosz, 1/4 grosz, 1/8 grosz, 1/16 grosz. Gold and silver forints were primarily used for foreign trade. Grosses and smaller denominations were used in domestic trade. King Sigismund's coinage had a significant impact on the monetary history of Poland.