Patek Philippe Annual Calendar 5250

Patek Philippe's 2005 Annual Calendar Ref. 5250 was one of the first wristwatches with a silicon escape wheel ever produced. It is the first member of their Advanced Research project.

Overview

In the 2000s, Patek Philippe set up an Advanced Research project to address the long-standing issues of isochronism and durability in watches. The main technology applied to this task was a proprietary alloy of silicon known as "Silinvar". The company proceeded steadily, producing first a Silinvar escape wheel, then a hairspring, an anchor, and a balance.

Ref. 5250 was the first Advanced Research watch, introduced in 2005. Cal. 315 S IRM QUA LU SI included a Silinvar escape wheel, making it one of the first watches ever produced with such a component. The display caseback includes a large "cyclops" magnifier to allow the owner to inspect this high-technology component.

Although it used these high-tech components, Ref. 5250 was nevertheless a Patek Philippe. It included their revolutionary annual calendar mechanism with day and month subdials inset at 10:00 and 2:00, a date window below the moon phase indicator at 6:00, and a simple "+/-" power reserve indicator at 12:00. The dial features Arabic numerals at 3, 9, and 12, applied markers at all other hours but 6, and a "railroad" seconds track. The hour and minute hands are leaf shaped and feature lume. It has a traditional Patek Philippe case in white gold, with long integrated lugs.

Reference: 5250 white gold, 100 produced Movement: Automatic manufacture movement: Caliber 315 S IRM QUA LU SI, 21,600 A/h Annual calendar module Silinvar escape wheel with Silinvar Spiromax balance spring Geneva Seal Case: White gold D 39 mm Sapphire crystal caseback with magnifying bubble Dial: Silver Functions: Hours, minutes, central seconds Annual calendar with day, date, month Moon phase indicator Limited edition: 100 pieces Successor: Patek Philippe Annual Calendar 5350