Folles and forgeries : an appraisal of the composition of Roman copper-alloy coinage of the mid-third to mid-fourth centuries A.D. from Britain
This thesis deals with the effects of the burial environment on complex copper-alloy coins and how these can result in non-representative data leading to erroneous numismatic interpretations. Three main periods of Romano-British coin copying are investigated compositionally in order to demonstrate the value of a more rigorous methodology. Samples from selected hoards are used to examine the period of Radiate copying (AD 270's - 280's), the period of Constantinian copying (c.AD 341-346) and the period of the 'FEL.TEMP.' copies (c. AD 354-364). In addition to this well preserved hoard material, a small hoard of corroded together Constantinian nummi from Richborough was analysed in its entirety and is compared with numismatically identical hoard material, together with excavated site finds covering all three periods. The problems of creating a suitable sampling strategy and the specific problems related to the sampling of ancient numismatic material are discussed. The topic of segregation in complex alloys is examined, followed by a discussion of corrosion theory. The analytical techniques employed in this study are atomic absorption spectroscopy and electron-probe microanalysis. The choice and limitations of these techniques are assessed for numismatic research. Segregation and corrosion studies on four Radiates demonstrates that these are seldom adequately overcome using the accepted 'non-destructive' analytical techniques. A 3-D spatial study of corrosion is conducted using computerised imaging and database links on the Richborough hoard. This suggests that the bulk composition of individual coins can be altered by corrosion even within a single hoard if the differences in preservation are sufficiently pronounced. The application of a well developed sampling strategies and appropriate analytical procedures can provide results of high precision for numismatic studies. Measured application of univariate and multivariate statistical methods are utilized in order to assess variations and similarities in the data sets. This approach has provided new information on the use of copper-alloys and the technology of coin production for both official Roman coins and their copies during this period.