Patek Philippe Perpetual Calendar | Ref. 3940J | 18K Yellow Gold

The Patek Philippe Perpetual Calendar 3940J features an 18-karat yellow gold case measuring 36 mm in diameter and just 8.8 mm in thickness. Powered by the ultra-thin automatic Caliber 240 Q, it is a masterpiece of horological engineering. The iconic layout perfectly balances sub-dials for the day/24-hour indicator, month/leap year, and date/moonphase.