This Patek Philippe Annual Calendar Chronograph reference 5905P-010 brought the brand's calendar chronograph into a larger and more contemporary form. Its self-winding caliber CH 28-520 QA 24H pairs an annual calendar with a flyback chronograph, a combination Patek reserved for a small line of modern references. The 5905 marked a turn away from the more compact 5960 it followed, and for a collector drawn to the brand's late complicated watches, that shift is exactly the point. In platinum, the case measures 42mm across and 14mm thick, giving the watch the scale its display demands without losing proportion. The black dial keeps the watch on the restrained side of the reference, even as the architecture is unapologetically modern. More than a successor, the 5905 established the shape of Patek Philippe's current annual calendar chronographs, carrying one of the house's most successful contemporary complications into its mature form.