New insights into the earliest brass coinage production through pXRF survey of the Ashmolean collection

There is now good evidence that surface X-ray fluorescence can return sound qualitative results about the nature of archaeological copper alloys, making it a useful tool for ‘alloy surveying’ within numismatic collections. Our understanding of the earliest brass coinages produced in the Graeco-Roman world is heavily reliant on legacy data from drilled samples taken at the British Museum in the late 1970s. The potential contribution of qualitative surface XRF data has been underappreciated here. We demonstrate the utility of such an approach through a portable XRF survey of 115 copper-alloy coins from first-century BC Asia Minor. First, by replicating the qualitative alloy determination—brass or bronze—of 17 coin types destructively analysed at the British Museum. Then, by highlighting the existence of four new brass mints, two new brass denominations, multiple unexpected materials, and the possibility of alloy experimentation at the Amisos and Epicteteis mints.