The Patek Philippe Aquanaut Luce Annual Calendar watch 5261R-001, housed in a 39.9 mm diameter case, houses a self-winding movement with a 21K gold central rotor and an annual calendar with moon phase display. This watch’s calendar display is reversed, presenting the annual calendar mechanism, a distinctive feature compared to other Patek Philippe timepieces with similar annual calendars. Date and moon phase apertures are located at 6 and 12 o’clock, respectively, while subsidiary dials for the day of the week and month are located at 3 and 9 o’clock. The moon phase display is exceptionally precise, deviating from the actual lunar cycle by only one day every 122 years.