This is a common and long-lived small, thin manual movement, produced since the 1970's to today.
Cal. 215 was designed as a successor to the classic Patek Philippe Calatrava hand-wound movement, Cal. 12-120. By the time Cal. 215 was introduced in 1974, that movement was 20 years old. Yet the same basic architecture was used, in an effort to retain the same look as the original. Cal. 215 was truly a replacement for both the larger Cal. 177, an F. Piguet Cal. 21 derivative used by the company in the 1970's as well as the line of smaller movements (such as Cal. 23-300) used for decades.
Cal. 215 is a traditional movement with a classic Patek Philippe look: It includes five bridges or cocks in the classic configuration, has 18 jewels, and measures 10 ligne (21.50 mm) in diameter and just 2.55 mm thick. One difference from tradition is the use of a single bridge over the fourth wheel and escape wheel.
This was the first movement to use Patek Philippe's patented Gyromax balance wheel at "high-beat" speeds of 28,800 A/h. Achieving this oscillation rate had long been a challenge for Patek Philippe, but it worked well with this calibre.
Cal. 23-300 was used in many watches, including the following popular references:
- Patek Philippe Calatrava 3796
- Patek Philippe Calatrava 3919
- Patek Philippe Calatrava 5123
- Patek Philippe Calatrava 5196
- PP 12-120, the 12 ligne predecessor
- PP 10-105, PP 10-200, PP 10-110, and PP 23-300, the 10 ligne predecessors
- Patek Philippe’s Bread and Butter: The caliber 215
- The Patek Philippe Ref. 3919: A Star in Soft Focus