Veritas Temporis Filia: Non-Destructive Analysis of Counterfeit and Regal Copper Coins from the Sloop-of-War HMS Swift (1770), by Means of SEM-EDAX and WDXRF

Abstract

Four British copper coins, three halfpennies and a farthing, recovered from the wreck of the sloop-of-war HMS Swift (1770), were analyzed. The application of scanning electron microscopy with the aid of an energy dispersive X-ray detector (SEM-EDAX), and wavelength dispersive X-ray fluorescence (WDXRF) allowed the determination, by nondestructive means, of a set of diagnostic features. The specimens identified as halfpennies present a dendritic microstructure, typical of a process of melting and casting, and a copper alloy with varying amounts of tin, zinc, iron and lead. The farthing, however, was struck from pure copper. These results indicate that the three halfpennies are counterfeits, probably made in the early years of the reign of George III.