This article explores the complex dynamics of financial innovation in early modern times, challenging linear models of temporal and spatial divisions that tend to shape our understanding of the evolution of financial systems. It supports the idea that innovation should be viewed as a non-linear and contextual process, involving diverse stakeholders and characterised by interactions and unexpected occurrences. The study focuses on the dissemination and trajectories of financial innovations, specifically the bill of exchange and its variation, the ricorsa, as well as the transferability and negotiability of commercial paper. It does so by investigating the interactions and exchanges between merchants and bankers from diverse backgrounds during the sixteenth-century Lyon fairs, using the archival records of one of the first Italian banks in Lyon (Salviati). The study reveals the mutual influence and acculturation among these agents and challenges the compartmentalisation of financial expertise. Through an analysis of transactions recorded in the Salviati bank's ledgers, the article highlights previously unknown uses of commercial paper by Southern merchant communities and discusses the factors that may have hindered the full-scale development of endorsement and discount in the Lyon trading networks, despite their potential benefits. The results provide insights into the intricate nature of financial innovation and the influence of structural and cultural factors on its development.