Archaeometallurgical study of Greek and Roman copper-alloy coins: A wide range of skills and techniques.

Compared to studies that already have tackled this topic but only for a specific coinage or period, our coins sample (135 coins from around the Mediterranean Sea and struck between 5th c. BC and 3rd c. A.D) allows to understand better the different coin manufacturing processes on a large geographical and chronological scale. Metallurgical investigations (metallographic observation, by optical and scanning electron microscopy) allows us to reconstruct the metallurgical history of these materials and to understand the savoir-faire used in their operational chain. The alloys used (mostly Leaded Bronze) are determined by X-ray fluorescence spectrometry in addition to Vickers hardness tests, allowing us to understand the impact of minting. The study has already highlighted recrystallized coins that involve mechanical and thermal treatments in their manufacturing process. The microstructure of these coins suggests a more complex metallurgical history than only casting and minting. This raises questions about the purpose and interest of this type of process for the craftsmen. Considering the geographical distribution of our samples, are there any similarities between their regions and years of issue? What about this distribution according to their categories and the different processes highlighted? Experimental archaeology sessions were carried out. The aim of these sessions was to investigate the relevance and implementation of some of the steps revealed by the analyses. Various treatments (mechanical, thermal) that may have been involved in the manufacturing process of ancient coins were investigated. Such as quenching, overstriking, or hot striking (still discussed today). In order to compare (in terms of microstructures and hardness) the results obtained from reproduced samples to archaeological ones. And, to assess whether these treatments have been implemented (or not).