This paper presents a stock flow model of two economies (together comprising the whole world) which trade goods and financial assets with one another. The accounting framework, though comprehensive in its own terms, is very much simplified (it has interest rates without interest payments and exchange rate changes without changes in relative prices) so as to reach the main conclusions as simply and easily as possible. The paper is (a contrario) critical of attempts to deploy open economy models which only analyse the operations of a single economy, without regard to the responses of the rest of the world. In particular, the paper is critical of the influential Mundell-Fleming (M-F) model and finds that the characteristic M-F results are confuted once a full set of double entry accounts is used with all processes firmly located in historical time.