Calibre 315 was an innovative movement on its introduction around 1984, replacing the ill-conceived Cal. 335 and 310. Although sharing its basic architecture with the 335, Cal. 315 was improved in almost every way. The most critical improvement was reduction in frequency to 21,600 A/h and more durable uni-directional automatic winding gears, addressing a critical issue in the 28,800 A/h Cal. 310. Later, 100 "Advanced Research" Cal. 315 movements were presented in 2005 with a silicon escape wheel and ceramic bearings. Although most watch models use the newer Cal. 324, a few continue with the now-venerable 315.
There is some controversy about the number of jewels in Cal. 315. Patek Philippe initially said the movement had 29 jewels, but later revised this to 30. Still later the company went back to saying it had 29 jewels. It is not clear what caused this discrepancy.
Calibre 330 is virtually identical to Calibre 315 apart from the location of the date: Cal. 330 includes four extra parts so the date could be narrower and recessed into the movement, although the date aperture is still located at 3:00. This gives Cal. 330 an overall height of 3.5 mm, rather than the 3.22 mm of Cal. 315.
Patek paired the slim Cal. 315 with various complication modules:
- Cal. 315 S C - Center seconds, date
- Cal. 315 S QR
- Cal. 315 S IRM QA LU - annual calendar, moon phase, power reserve indicator
- Cal. 315 S IRM QA LU Si - Advanced Research silicon escape wheel, annual calendar, moon phase, power reserve indicator
- Cal. 315/136 includes a retrograde date, month, moon phase, and perpetual calendar
- Cal. 315/290 includes a calendar module
- Cal. 315/299 includes an annual calendar module
Patek Philippe began an Advanced Research program in 2000 to invent new watch components and approaches. One of the first fruits of this labor was the development of a silicon escape wheel. They found that this wheel, paired with traditional ruby escapement pallets, had the same friction characteristics as lubricated steel but needed no lubrication. This was paired with lubrication-free ceramic ball bearings for the winding rotor and produced in limited numbers as calibre PP 315 S IRM QA LU SI. 100 special Advanced Research watches, Ref. 5250 were produced with this movement, and these included a special "loupe" on the rear sapphire crystal so the silicon escapement can be viewed.