X線残留応力測定による古貨銭の偽造に関する調査

抄録

There is historical evidence that Japanese coins were imported from China from the 12th century for about 600 years. These coins stayed in circulation until the 18th century. During the period, daimyos and influential persons such as merchants energetically minted imitations of inferior quality in order to make higher profits as well as to supplement the lack. Some of these imitations had the marks of rulers or technicians minting these coins and, ironically, are valuable in their own right due to their historical value. The market for these marked original imitations has resulted in original, unmarked coins being marked and sold as original imitation coins. Unfortunately the conventional X-ray fluorescence analysis cannot tell whether the mark is authentic or made after minting the imitation coin. In this study, we tried to apply X-ray stress measurement to the analysis of differences between an authentic coin and a counterfeit coin. The primary elemental composition of two kinds of old coins of “Shofu Tsuho” originating from the Shofu Era of the Chinese Northern Sung Dynasty were determined by the X-ray fluorescence analysis. For Cu element of the major elements, the difference between the authentic coin with the mark and the counterfeit coin with the same mark was evaluated by the residual stress and the work hardening of the marked area using X-ray residual stress measurement. Herein we report the results of the analysis.