The technical details can be found on Ranfft’s website on the pages of the ETA 2391.
Hand-wound centre-seconds indirectly driven minutes movement. The movement is just 3.6mm thick.
Full movement
Underside of the barrel bridge with the click and its spring
Barrel bridge removed
Gear train bridge removed
The fourth wheel is at the centre whereas the centre (now main) wheel is near the edge of the movement
The long escape wheel pinion is driven by the fourth wheel
The third wheel pinion reaches down to the main wheel, but also is partly exposed on the dial side, driving the friction wheel and through it the cannon pinion
Dial
Dial removed
Hour wheel removed
Intermediate wheel cover removed
The intermediate wheel interacts with the cannon pinion, not the friction wheel. This allows the setting of the time without damaging the movement
The friction wheel around the cannon pinion drives it during normal operation, but slips when the time is being set.
The third wheel pinion peeks through the base plate and drives the friction wheel
Friction wheel removed unveiling the third wheel pinion
Main wheel
Third wheel with its long pinion interacting with both the main wheel on the top plate and friction wheel on the bottom (dial) plate
Fourth wheel with a long staff carrying the seconds hand
