Despite the lack of political accountability,ancient autocracies maintained a level of monetary stability that rivals mod democracies.This paper hypothesizes that it is the threat of counterfeiting that has constrained currency debasement.Unwilling to share seigniorage with counterfeiters,who are active only if currency is debased,the govment refrains from debasement unless in extreme fiscal situations.To document the facts,we build a database of historical Chinese copper coins that covers the period from the Qin dynasty (221 BC-207 BC) to the Republic of China.We also use the introduction of the steam press in late Qing China as a natural experiment to test the theory.The steam press produced coins of fine patts that counterfeiters were unable to mimic.As the theory predicts,the removal of the threat of counterfeiting triggered the most serious debasement in the history of the Qing dynasty (1644-1912).