This dataset is published in conjunction with the article Seppo Eskola, Jaakko Tahkokallio: "How many fragments? The original extent, the nineteenth-century losses, and the present size of the Swedish-Finnish medieval book fragment collections", SKHS 2024. It consists of three data files (csv format), an appendix (pdf format) with tables summarising the data, and a readme file. Data_1628 contains data on the Vasa-era regional accounts of the Swedish realm, as listed in their 1628 catalogue, and their parchment covers. Data_1637 contains data on the accounts of the central administration, as listed in the 1637 catalogue, and their parchment covers. Data_Fragments itemises each manuscript and early print fragment held by the National Archives of Sweden and the National Library of Finland. More detailed information is given in the readme file and in the published article.