Cartier Rotonde de Cartier Perpetual Calendar Watch - 40.5 mm Gold Case - W155621840. 5 mm by 13 mm thick 18K gold case, sapphire back, beaded crown set with sapphire cabochon, sapphire crystal, white dial with silvered open work grid, Roman and Arabic numerals with blued hands, caliber 9422 MC automatic movement with perpetual calendar complication, days indicated by a retrograde hand, months and leap years in a counter at 12 o'clock, black alligator strap with 18K white gold buckle, buckle double deployant. Water resistant to 30