====== Patek Philippe Annual Calendar 5250 ======

{{wst>image_cr|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 [[Patek Philippe Advanced Research|Advanced Research]] project.

===== Overview =====
In the 2000s, Patek Philippe set up an [[Patek Philippe Advanced Research|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]]. [[PP 315|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.


<WRAP ud ud_mod>

**Reference:**
  * 5250 white gold, 100 produced

**Movement:**
  * [[Automatic]] [[manufacture]] movement [[PP 315|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]]
</WRAP>

{{tag>Watch_models Watches_with_annual_calendar Patek_Philippe_models Patek_Philippe_references Patek_Philippe_Advanced_Research_models}}