From collection or archaeological finds? A Non-Destructive Analytical Approach to Distinguish between Two Sets of Bronze Coins of the Roman Empire.

This study stems from the need to establish whether there may be relationships between a group of 103 bronze coins from the Roman era found in archaeological excavations on the Cesén Mountain (Treviso, Italy) and a group of 117 coins kept at the Museum of Natural History and Archaeology in Montebelluna (Treviso, Italy). Only non-destructive analytical techniques were used to characterize the surface of the six coins blindly taken from the two sets. The elemental analysis of each coins’ surface was carried out by µ-XRF. To better observe the morphology of the coins’ surfaces, SEM-EDS was used. Compounds covering the coins coming from both corrosion processes (patinas) and soil’s encrustations deposition were also analyzed by means of FTIR-ATR technique. The molecular analysis confirmed the presence of silico-aluminate minerals on some coins, unequivocally indicating a provenance from clayey soil. Some soil samples, collected from the archaeological site of interest, were analyzed to verify whether the encrusted layer on coins could contain chemical components compatible with them. This result, together with the chemical and morphological investigations, lead us to subdivide the six target coins into two groups. The first group is made up of two coins coming from the set of coins from excavation (found out in the subsoil) and from the set coming from open air finds (coins found at the top layer of the soil). The second group is made up of four coins which are devoid of the characteristics corresponding to an exposition to the soil contact for long periods of time and, moreover, their surface compounds could suggest a different provenance. The analytical results of this study support numismatists that were unconvinced of considering all coins coming from the same finding site only on the basis of archaeological documentations.