Zenith caliber 18.5 is Swiss movement from 1910’s.
Functions: hour, minute and sub second.
This movement is used on pocket watches, open face.
Manual-winding movement with 15 jewels (with breguet hairspring).
f = 18000 A/h
Power reserve: 36 hours
Diameter: 41.25 mm
Other links:
Zenith caliber 18.5 watch parts