The 5726A-001 expanded the Nautilus into more complicated territory when it debuted in 2010, marrying Gérald Genta's iconic 1976 sports design with Patek Philippe's patented annual calendar. The annual calendar itself — a Patek invention of 1996 — represents one of the maison's signature contributions to modern watchmaking, automatically accounting for months of thirty and thirty-one days while requiring correction only once a year. For collectors, the reference offers a compelling balance: the everyday wearability and unmistakable identity of the Nautilus combined with a genuinely useful complication, executed in steel and offered on a leather strap rather than the familiar integrated bracelet. The 40.5mm case in stainless steel measures 11.3mm thick, retaining the signature rounded octagonal bezel with alternating satin and polished finishes. The sunburst charcoal grey dial with black-gradient rim carries horizontal embossing, white gold applied baton markers, and luminescent hands, with day, date, and month apertures beneath twelve and a combined moon phase and 24-hour subdial at six. The self-winding Caliber 324 S QA LU 24H/303, visible through the sapphire caseback, delivers a 45-hour power reserve, completed by a black alligator strap with fold-over deployant clasp. *This timepiece comes with the Patek Phillipe stylus and original tag. Reference Number: 5726A-001 Model Family: Nautilus Movement: Automatic Case Material: Stainless Steel Bracelet Material: Leather Strap Dial: Black Case Dimension: 40mm Year: 2022 Condition: Pre-Owned (Very Good) Box & Papers: Original Box, Original Papers