IWC Portuguese Perpetual Calendar 18K Yellow Gold IW502213. Box & Cert Dated Aug 2013. 18K yellow gold case 44.2 mm, sapphire-glass back, automatic winding calibre 51610 movement with power reserve display, perpetual calendar with displays for the date, day, month, year in four digits and perpetual moon phase, small hacking seconds, Glucydur* beryllium alloy balance with high-precision adjustment cam on balance arms, Breguet spring, rotor with 18-carat yellow gold medallion, approximately 7 days of power reserve, original dark brown alligator leather strap fitted with original 18K yellow gold deployant buckle.