In the archives of Yale University, there's a 367-year-old bond from the water authority of Lekdijk Bovendams, in the Netherlands. And it's still paying interest.
Thanks to:
Prof. Geert Rouwenhorst for his time and explanation
All the team at the Beinecke Rare Book and Manuscript Library
Michelle Martin (@mrsmmartin) for editing the interview
and Leendert van Egmond for telling me about the bond!