To get a proper caliber number for a Geneva Sport movement is very difficult, since the online and offline literature for this mystic manufacturer differ.
The 11 1/2 ligne movement shown here is most likely a Geneva Sport 51, even though it is marked as “GSW 40,41”. Since the base plate look the same for both caliber families and the movements only differ in the bridges, it is quite possible, that they just used the same base plate for them.
All important bearings contain rubies, the minute wheel lacks a ruby on the dial side, but has got one on its bearing cock in the movement side.
With the centrally beared (under its own cock) minute wheel, this movement represents more or less state of the art of the 1960ies.
The Geneva Sport 51 has got a directly driven center second hand.
In the 21 jewel version shown here, the bearings for the third wheel, seconds wheel and escape wheel are covered with cap jewels, as well, as the dial side bearing of the escape wheel. With them, the high number of 21 jewels was achieved.
The two leg screw balance is not yet shock protected. It still beats slowly with 18000 A/h, which can be adjusted on the hairspring key only.
As escapement, a classical swiss pallet lever escapement was used.
On the dial side, the balance wheel bearing is covered with a simple cap jewel (inserted in a long plate, like the cap jewel for the escape wheel). You can also see the preparations for a cap jewel for the third wheel.
This copper toned movement has got a yoke winding system.
|Number of jewels:||21|
Nickel screw balance|
|Balance bearing / direction hairspring:||Clockwise|
|Adjust mechanism:||Hairspring key|
|Construction type:||solid construction|
|Winding mechanism:||yoke winding system|
|Setting lever spring:||3 hole(s)|
|Functions:||hour, minute, second|
|Size:||11 1/2''' (measured: 25,6mm)|
Flume: K2 -|