Methods
SEM microscopy coupled with EDS elemental spectroscopy for complex microstructural characterization and XRD for phase identification. Three distinct types of forgery methods were identified: the amalgam method is the first used for copper blank silvering (1620), and immersion in melted silver (1621) is the second one. Both methods were used to forge coins with proper legends and inscriptions. The third method is the tin plating of copper coins (with corrupted legend and altered design) (1622, 1623, and 1624). The EDS investigation revealed Hg traces inside the compact silver crusts for the first type and the elongated silver crystallites in the immersion direction, which are well-attached to the copper core for the second type. The third forgery type has a rich tin plating with the superficial formation of Cu6Sn5 compound that assures a good resistance of the coating layer. Therefore, this type should have been easily recognized as fake by traders, while the first two types require proper weighing and margin clipping to ensure their quality.