In 1926, François Machon, a Swiss physician who lived for many years in Argentina, organised the restitution of a religious garment that had been stolen from the cathedral of Paraguay in the late 1860s and was kept in the Swiss Musée d'ethnographie de Neuchâtel (MEN) in exchange for a small part of his ethnographic collection. In the following decade, he donated more of his own collections to the MEN, but also negotiated as a go-between for the donation of his son (...) Roger's collections. On one occasion he managed, again, to arrange the exchange of a proto-historic Swiss lake-dweller axe for a small collection of Amerindian artefacts. The Machons' case sheds light on the logics of donations of a private collection holder, his tactics and strategies of persuasion, and his entangled web of affects, straddling two countries and two networks of fidelity in a context of migration. It also helps us understand the complex rationalities of acquisition and the polysemy of a peripheral municipal cultural institution. This case informs us about the rationales of a peripheral museum and on the criteria used to assess the quality of donators and their collections; it illustrates the asymmetry of the exchange values of European and South American, ancient and contemporary, artefacts, and the unequal vocality of the different actors. Similarly, it gives us a perspective on the rationales that were mobilised to justify giving away parts of its collections. The exchange of artefacts between the Machons and the MEN helps us understand museums not only as patrimonial of scientific institutions, but also as economic actors, whose agents convince, gamble, bargain, and negotiate, and try to make best use of their resources, symbolic and monetary, to increase their assets and social benefits. (shrink)