Several kinds of analyses were used to investigate trends in the composition of silver coins of Egypt during the first three centuries B.C., the period of the Ptolemaic inflation. The goal was to chart the stages by which the purity of the silver coins was debased during the period. While wet chemical analysis and deuteron activation analysis were used as adjuncts, most of the data were obtained by neutron activation analysis, exact procedures for which are described in an appendix authored by I.D. Brown and H. Lycklama. It is assumed that copper content is a good measure of extent of debasement. Before 148 B.C., very low copper content characterized all examined coins. Between 136 B.C. and 148 B.C., copper content rose to about 2 percent, while gold remained stable. Wide variation in copper content characterized coins made between 136 B.C. and 51 B.C., with an average of 8.4% copper. Finally, after 51 B.C., Cleopatra VII issued staters that were 2/3 copper and 1/3 silver. All in all, silver coinage in Egypt was remarkably stable during this period. The very striking debasement of 51 B.C. is seen as an aspect of the general reform of the currency that was undertaken at that time. The analyses also indicate a date of 263 B.C. for the beginning of the 'Civic Era', about which there had previously been much speculation.