The 10 1⁄2 ligne Osco 300 is part of the large movement series, which Osco launched in the 1060ies.
The caliber 300 uses an indirectly driven center second, which is beared under an own and well executed cock.
Unlike the simpler models of the caliber family, all important bearings contain rubies. Nevertheless, the construction principle - a pillar construction with a rocking bar winding system - is used here, too.
Due to the pillar construction, the gear train builds pretty high. It consists of the mainspring barrel, which drives the center minute wheel, followed by third wheel, seconds wheel and steel escape wheel, whose bearing has got even a cap jewel on the movement side.
The axle of the third wheel is prolonged, on its end on top of the upper gear train bridge, there’s the transmission wheel, which drives the center second. Its gear is beared under an own cock, which is secured by two screws - pretty costly.
A friction spring adds a little tension and avoids fluttering of the second hand.
The slim anular balance beats slowly with 18000 A/h. She is beared in two KIF Trior shock protections. The effective length of its hairspring can only be adjusted with the hairspring key only. This was usual in the price range of these watches.
Since the Osco 300 uses a rocking bar winding system, the ratchet is located on the dial side and here it has got a very well executed true pawl.
In general, the dial side makes a pleasantly tidy and clean impression, which is not necessarily a matter of course for a pillar factory.
|Number of jewels:||17|
Nickel anular balance|
|Balance bearing / direction hairspring:||Clockwise|
|Adjust mechanism:||Hairspring key|
|Construction type:||pillar construction|
|Winding mechanism:||rocking bar winding system|
|Setting lever spring:||1 hole(s)|
|Functions:||hour, minute, second|
|Size:||10 1/2''' (measured: 23,3mm)|
Flume: K3 34|