Sieber is known primarily as a talented interpreter of Ricardo and Marx. However, in his intellectual biography there is the second significant contribution that hasn't been adequately discussed from modern positions yet. Sieber wrote his «Essays on the Primitive Economic Culture» (1883) (more than five hundred pages treatise) during the second phase of his life - emigration to Switzerland. The article attempts to evaluate this work, answering the following questions. What is the contribution of Sieber to the economic anthropology? What is the place of Sieber in classical discussions that took place within the framework of economic anthropology? What Sieber meant by economic culture? What are the results he has come to and what are the methods he used? How Sieber studied the synthesis of history, law, society and the economy? What is the additional value of his biography in capturing Sieber's ideas? The paper shows that Sieber can be described as an armchair scholar. Marcell Mauss is the closest example. Sieber examines the elements of the economic culture of primitive society, skilfully using multiple eyewitnesses. He is focusing also on the archival residuals in later civilizations and even in the present. The cases provided by Sieber made think he is not so close to an evolutionary approach, so fashionable in the nineteenth century. He describes the institutions and the structure of labor relations, production, consumption and redistribution. Particular attention is paid to his views on cooperation, gift and property. Thus, Sieber fills the gap in the Marxist doctrine as well as he outlines the important generalizations, that in the twenties century formed the new discipline of economic anthropology.