A tattoo on the wrist of a wealthy merchant in a 17th-century group portrait is the only one ever found in depictions from that era and may well be the oldest in Dutch painting, experts from the Amsterdam Museum have said. The painting, the Oppercommissarissen der Walen, attributed to Wallerant Vaillant, shows a group of prominent citizens in charge of the city’s harbour, quays and cranes. Among them was rich merchant Wesssel Smits, who has now been found to sport...