The present paper is a publication of a collection of the coins of Hellenistic Cappadocia held by the State Historical Museum (Moscow). This collection consists of 37 items: 36 drachms and a tetradrachm, including rare and unique specimens. The coins under investigation relates to the coinage of Ariarates IV, Ariarates V, Ariarates VI, Ariarates IX, Ariobarzanes I, Ariobarzanes III and Ariarates X. A great part of these items derives from the acquisitions of the late XIX – early XX centuries. Unfortunately, the precise information about its provenance is unavailable. Ten pieces were received by SHM after 1945 and come from private collections of various collectors. 24 items out of 37 belong to the reign of Ariobarzanes I and represent coins of the same denomination – drachm. A relatively chronologically representative sample made it possible to analyze the surface composition of the metal alloy of coins by X-ray fluorescence analysis. The results show that by the end of reign of Ariobarzanes I the percentage of silver in the coin decreases while the proportion of copper increases. The correlation analysis demonstrates a very high level of inverse correlation between silver and copper, which means that the "spoilage" of the coin took place precisely due to an increase in the proportion of copper, and the trace impurities of other metals found in the metal were not included in this process. It could be assumed that such a decrease of proportion of silver in the coins of Ariobarzan I was caused by the difficult financial situation of Cappadocia at the end of the Third Mithridatic War.