The “Powerwind” caliber 917 debuted in 1954. Like all Mido movements, it is not a true inhouse caliber, but an AS ebauche, exclusively produced for Mido.
The Cal. 917 used a rotor mechanism, which winds efficiently in both directions and gives enough powers even when not worn very long.
The movement is a quite standard 17j movement with indirect center second hand and date indicator without fast-setting mechanism.
To achieve best precision rates, Mido used the Incastar system, which allows a free swinging hairspring without inprecise regulator pins. The effective length of the hairspring is set with the knob, which clamps the hairspring between two roles. Because of that, the beat synchronity has to be adjusted in a second step, too. Since this is a bit time-consuming, the interesting Incastar mechanism was not used in many consumer watches, but only in better watches.
|Number of jewels:||17|
Glucydur screw balance|
|Balance bearing / direction hairspring:||Clockwise|
|Functions:||hour, minute, second, day, selfwinding|