The supremacy of private creditor interests over sovereign government debtors has resulted in radically different economic outcomes in moments whose structure is otherwise quite similar. In this paper, I argue that understanding these outcomes requires us to revisit the properties and function of money under capitalism. Drawing upon heterodox monetary and Marxist theorists, I characterize capitalist money as a zone of contestation where governments and private interests fight over the legitimacy and monetization of private “promises to pay.” I work to establish an unusual formal parallel between the genesis of capitalist banking in England and the political economy of modern Argentina in order to show how seemingly similar political and economic logics can result in either prosperity or ruin depending upon whether the co-constitution of capitalist money by governments and private actors results in a mutually beneficial symbiosis or a cycle of distrust and exploitation. These outcomes depend upon the results of both structural and epistemic contestations which underlie capitalist money itself.