This chapter presents evidence of annotation and provenance as discovered in the mathematical texts of the Rare Books Collection of the Science Museum, London. In particular, it draws from a copiously-annotated, 1685 copy of John Seller’s A Pocket Book, containing Several Choice Collections (1677), analysing this volume as means to consider how readers' marks can contribute to our understanding of the use and collection of mathematical materials in the early modern period. At first glance, Seller’s A Pocket Book offered its readers a range of arithmetical, geometrical, and trigonometrical tools, and was intended to be consulted for action by sailors, merchants, and gaugers alike. Its contents are therefore demonstrative of the ‘useful’ mathematics a less-numerate occupational group might require to undertake a number of activities. The annotations contained therein, however, evince users’ idiosyncratic responses, ranging from copying, to correction, to the creation of a repository of mathematical and intertextual information: all within a single text. I argue that by understanding Seller as a producer, together with his readers as consumers, we may further deepen our understanding of the use and value of mathematical practice in late seventeenth-century English culture.