The chemical composition of silver coinage under the Roman Republic has been little studied. The largest recent survey is that of Holstein (2000), involving the analysis of 590 coins. The main analytical technique used was electron-probe micro-analysis (EPMA) directly on unprepared surfaces, which was unable to overcome surface effects that produced enhanced silver levels and reduced copper levels unrepresentative of the original compositions as well as alterations to the few trace elements measured. Comparisons carried out at the time by the British Museum Laboratories (Cowell and Ponting 2000) revealed the extent of the problem and how this potentially masked important compositional variations.
As part of the ERC-Funded RACOM project (835180 RACOM ERC-2018-ADG), over 1000 Roman Republican silver coins from c. 150 BC to the Augustan period have been sampled by drilling and analysed by microwave-plasma atomic emission spectrometry (MP-AES). This paper presents the preliminary findings and interpretation of these data.