This article examines sovereign creditworthiness concerns and policies in a Latin American country that needed economic development and stabilization financing from bankers, the International Monetary Fund, and the World Bank during the early years of the Bretton Woods era. It underlines the significance for developing country foreign financing breakthroughs of applying sound, coherent, and sustainable macroeconomic policies; of credible and professionalized state institutions; of adhering to formal and informal rules of mainstream international finance; and the policymaking role of trustworthy economic teams coming from the local establishment who endorsed foreign financiers’ ideas and recipes. While written from the perspective of economic history, the analysis incorporates recent insights from earlier historical periods and worldwide case-studies, and of specialists in international political economy and credit rating studies.