Investigation of Contemporary Forgeries of Ancient Silver Coins

Abstract

Four ancient Roman silver coins from about 200 BC to 200 AD, mainly contemporary forgeries, were investigated in order to deduce the methods and materials used in the production of the forged coins. Special attention was devoted to a Denar from the Roman Republic, a C. Mamilius Limetanus denarius serratus (approx. 82 BC), because an original coin (pure silver) as well as a forgery were available. These coins both show serrated edges, i.e. notches all around with irregular spacing. A combination of microbeam analytical techniques was applied: Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA) and Secondary Ion Mass Spectrometry (SIMS). Some of the counterfeits consist of a base metal core plated with silver. The serrated Denar exhibits a plating layer with a thickness of approx. 100 µm as determined by SEM and SIMS. This is an indication for foil silvering, as well as the apparent overlapping of the outer layer in one particular area.