A ref. 5140J, the last in a long line of Patek Philippe’s automatic Perpetual Calendars, a line that is widely considered to be their first serially produced, truly complicated watch. First introduced in 2006, it took over the throne from the 3940, now widely considered one of the most important watches in Patek’s modern history. The 5140 continued the legacy of the micro-rotor calibre 240 Q, but changed in many small details. Today, it is the standard to which all other modern automatic perpetual calendars are measured.