Zenith EL PRIMERO 21 9004 Mode D'emploi page 9

This means that the time display and chronograph each have
their own completely independent mechanism with its own
barrel and high frequency escapement.
For the chronograph, this oscillates at a breathtaking 50 Hz
(360,000 VpH). As standard for the El Primero, the time display
calibre oscillates at 5 Hz (36,000 VpH).
Key features
El Primero 21 (Calibre 9004)
Diameter: 32.80 mm (14 ¼)
Thickness: 7.90 mm
Number of components: 293
Number of jewels: 53
2 barrels:
> Watch power reserve: 50 hours
Frequency: 36,000 VpH (5 Hz)
> Chronograph power reserve: 50 minutes
Frequency: 360,000 VpH (50 Hz)
Unidirectional automatic winding for the watch and manual winding for
the chronograph.
Functions:
> Hours, minutes and seconds
> 1/100th of a second central chronograph
30-minute counter at 3 o'clock
60-second counter at 6 o'clock
Chronograph power reserve at 12 o'clock
5 <