In this paper I describe a ?monetary? system in which backing is provided for the government?s liabilities by way of contingent resort to taxes. The system has some of the features of a commodity money system with a large seignorage spread between bid and ask prices. It is studied within the context of a one-good, pure exchange model of two-period-lived overlapping generations in which, aside from various uniform boundedness assumptions, considerable diversity is allowed both within and across generations. Two results are established: (i) the existence of at least one perfect foresight competitive equilibrium, and (ii) the Pareto optimality of any such equilibrium.