The “Treasure of Como” and the Production of Solidi During the Late Roman Empire

The Como Treasure, discovered in 2018 during archaeological excavations in the Roman town of Novum Comum, consists of 1,000 solidi and a few other gold artifacts – three rings, a small piece of an ingot and incomplete and unfinished gold jewelry. It is the most important hoard of Roman gold coins discovered in Central/Western Europe in recent decades. The examination of the solidi allowed for the study of the traces of workmanship and the reconstruction of the operative chain used in Late Antiquity mints. The gold was melted under oxidizing conditions, purified by cupellation and cementation and then assayed. In order to obtain the blanks, foils were made, cut in round plates with iron shears. Then the edges and the weight were adjusted al pezzo with iron files. As some of the impurities visible to the naked eye show on some coins, iron filings from files accidentally got into the filings or gold waste used for melting. Coins were obtained by minting using dies engraved according to a well determined sequence: after a subdivision of the die’s surface with compasses, the figures and finally the inscriptions were engraved. The production process was concluded by checking the weight of the coins. In times of intensive production mints could shorten their production times by recoining old coins. In this case, the purity of the gold was checked by taking a sample from the center of the coins before their recoinage. These different stages required specialized staff and ateliers with different features placed in a building that guaranteed high levels of security and that was well connected to the road network to allow supplies. These characteristics seem to be found in a building unearthed in old excavations in Milan and already interpreted as a bath. On the basis of the information currently available, however, the possibility of it being the mint of the comitatus cannot be ruled out.