This paper examines medical scientists’ accounts of their rediscoveries and reassessments of old materials. It looks at how historical patient files and brain samples of the first cases of Alzheimer’s disease became reused as scientific objects of inquiry in the 1990s, when a genetic neuropathologist from Munich and a psychiatrist from Frankfurt lead searches for left-overs of Alzheimer’s ‘founder cases’ from the 1900s. How and why did these researchers use historical methods, materials and narratives, and why did the biomedical community cherish their findings as valuable scientific facts about Alzheimer’s disease? The paper approaches these questions by analysing how researchers conceptualised ‘history’ while backtracking and reassessing clinical and histological materials from the past. It elucidates six ways of conceptualising history as a biomedical matter: scientific assessments of the past, i.e. natural scientific understandings of ‘historical facts’; history in biomedicine, e.g. uses of old histological collections in present day brain banks; provenance research, e.g. applying historical methods to ensure the authenticity of brain samples; technical biomedical history, e.g. reproducing original staining techniques to identify how old histological slides were made; founding traditions, i.e. references to historical objects and persons within founding stories of scientific communities; and priority debates, e.g. evaluating the role particular persons played in the discovery of a disease such as Alzheimer’s. Against this background, the paper concludes with how the various ways of using and understanding ‘history’ were put forward to re-present historic cases as ‘proto-types’ for studying Alzheimer’s disease in the present.