Apprehend the Coin Metal Supply during the Fourth Century AD-Analyses by Portable X-ray Fluorescence Spectrometry of Nummi from the Saint-Germain-de-Varreville (Manche)

Among the thematics studied in numismatics using archeometry specific research on the stock of metal struck in the 4th century turns out to be fascinating but complex. Influx of new metallic resources, voluntary recasts of coins: these phenomena have great consequences for the coinage produced in all the workshops throughout the late Roman Empire. Some of these data can be measurable. Metallic alloys (coins in this case) contain minor or trace elements that constitute a kind of "identity card" the supply of monetary workshops. Ten years ago, Isabelle Bollard andjean-Noel Barrandon collected several analyzes of bronzes struck during the 4th century. Our own observations, obtained within the FANUM project, funded by the Normandy region, on 14,528 coins (nummi) of the Constantinian period contained in a fortuitously discovered treasure in Saint-Germain-de-Varreville (Manche) have motivated a thorough new study of the alloys used during this period focusing on the traces of gold an d silver. Indeed the variety of workshops represented in the treasure has encouraged such an inquiry. The choice of portable X-ray fluorescence has enabled to develop a protocol of analysis adapted to a large number of coins. The use of 774 analyzes carried out on nummi struck in the Western workshops has completed previous works, but also enabled to highlight the use of different metal stocks from the 320s.