The research documented here was undertaken by Angéline Rais during her fellowship at EXC 2020, within Research Area 4 'Literary Currencies', between January and March 2024. Her project investigated the role of German antiquarian booksellers in valuing medieval works in the first half of the twentieth century. This period is significant because it shows how members of the trade shaped the way European medieval book heritage was perceived as research objects and goods to sell. Dealers promoted the scholarship on rare books by compiling modern catalogues, hiring specialists in medieval and literary studies, publishing journals and monographs, and sharing their expertise with clients. The correspondence between Erwin Rosenthal (1889–1981) and Martin Bodmer (1899–1971) exemplifies these exchanges as they examined the scholarly and financial values of a manuscript of the Nibelungenlied.