Classification of counterfeit coins using multivariate analysis with X-ray diffraction and X-ray fluorescence methods

Abstract

Counterfeit coins (277 samples) were analyzed by both X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods without any pretreatment. The counterfeit coins were clearly classified into two groups using cluster analysis (CA) and principal component analysis (PCA) for XRD peak patterns. One group (250 samples) was made by a pressed method and another one (27 samples) was made by a nickel-plated method. Using four elements (Cu, Ni, Fe and Zn) and obtaining XRF for 257 samples, they could be divided into four groups by CA. On the other hand, they were classified into five groups using their diameter, thickness, weight, density, density/thickness and density/weight. The latter classification method would suggest something of a change in the process of the pressed method.