Objects are telling of identity and difference, through possession, exchange, and display, but this dynamic must be historicised and socially situated. In this article, I focus on the signification of ethnicity in Vietnamese museums, particularly on an apparent distinction between historically ‘hot’ and ‘cold’ matter. The earliest displays responded to the previous hegemony of French colonial significations. Subsequent national exhibits consistently enable Vietnam through assemblies of objects and images, but suggest—when examined over time—fundamentally different configurations of the nation, ethnicity, gender, and historicity. Object assemblies, where a centrepiece signifies the surrounding objects, indicate repeated prospecting for new social assemblages, most recently situating Vietnam in post-Cold War networks through the Southeast Asian kinship implied in the nation’s ethnic diversity.