In this case study, Proton-Induced X-ray Emission (PIXE) analytical technique has been applied to thirtyeight Iranian silver coins, selected from a private collection. The purpose was to study the fineness evolution from beginning of the 13 to the 16th century AD in Iran. The content and variation of metallic and nonmetallic elements Fe, Cu, Zn, Ag, Au and Pb were observed. It was found that Cu, Pb, Zn and Au were mainly present along with silver as major component. The content of Ag as the main constituent of the coins varies from 55 to 97 %. This significant variation in the content of the major constituent reveals the economical difficulties encountered by each dynasty. It could be also attributed to differences in the composition of the silver mine used to strike the coins in different locations. The results offer valuable information about the economy of the periods under study.