This is the Audemars Piguet caliber 2508quartz watch movement. This ultra thin caliber stands only 1.6mm tall and can be found in Royal Oak 2508 watches.
According to Audemars Piguet, the accuracy of the quartz caliber 2508 is +/-2 minutes per year.
Battery Power Reserve
A fresh battery should last for a minimum of 30 months. The battery cell is a number 321 or 377 depending on the watch model. Both of these cells have a diameter of 6.80mm, but the thickness differs: 1.65mm vs 2.60mm. Both battery cells have a voltage rating of 1.55 V.
Time Setting Instructions
The AP caliber 2508 only has two crown positions. Pull the crown out (or unscrew the crown, then pull) one click for time setting mode.
In Audemar Piguet’s Own words:
“Quartz is a dominant element at Audemars Piguet. Used for the first time in the 70s, it completely revolutionised the notions of horological precision. Despite its superior performance, quartz technology does not enjoy the same prestige as mechanical watchmaking. However, in deciding to optimize the performance of its electronic movements, Audemars Piguet revives the glory of this advanced technology which enables the creation of ultrasophisticated instruments for professionals.”
AP Explains the technology:
“From the technical point of view, quartz movement are based on a regulator (the time-measuring element) consisting of a quartz crystal through which an electric current is passed. This “resonator” vibrates at an extremely high frequency (32’768 Hz), dividing the time into equal intervals. In an analogue display quartz watch, an integrated circuit records the electric signals transmitted by the quartz oscillator and divides their frequency into pulses equivalent to one, five or ten seconds.” -AP Quartz Movement Instructions for Use Manual