EPMA Investigation of Roman Coin Silvering Techniques

Ancient Roman silver coins, especially forgeries, contain various amounts of silver on the surfaces. The state of preservation of the outer layer can vary strongly among different areas of the same coin, thus an investigation of the entire surface is indispensable. The measurement of the silver distribution is a first step towards uncovering the manufacturing techniques. Element mapping by electron probe micro-analysis (EPMA) with increasing step size allows a survey of the complete coin surface. The suitability of this approach is shown and applied to coins having a dark optical appearance and unknown minting technique.