In the late 1950ies, Otto Schlund (Osco) launched the movement family 100, a series of 10 1⁄2 ligne movements with different features and swiss pallet lever escapement and a screw less anular balance, which was very modern at that time.
The Osco 107 shown here is the sister movement of the Osco 108, lacking the date indication feature, but instead it has got a decentral seconds indication a 6 o’clock.
This movement is a pillar construction; the ratchet is on the dial side.
It uses only eight jewels, four for the balance wheel bearing, one for the ellipse, one for the movement side bearing of the escapement wheel and two jewels of the lever pallets.
We’ve got a classical one-storey construction, almost a bit old-fashioned at that time, but often used, escpecially on simpler movements.
The screw-less anular balance has got two slightly waisted legs and is beared in two Monorex shock protections. It beats slowly with 18000 A/h.
On the dial side, you can easily spot the rocking bar winding mechanism and the ratchet. The latter one has got a genious spring construction:
The spring is held in place by the ratchet screw and interferes with the dot on top of the ratchet. The big advantage of this construction is, that you don’t have a flying spring here. The downside is, that a broken spring requires a spare part of the manufacturer.
In the lab
The specimen shown here was in a watch, which shows many signs of heavy use, there are even deep scratches on the dial.
Nevertheless, right from the start it showed a very good performance, slightly too fast, so that a service was not neccessiary. After disassembly, it was slightly oiled and adjusted.
Timegrapher resultThe rates are really good for a movement without service, only the bad balancing of the balance wheel and the resulting positional errors are a bit bad. But it nevertheless shows a perfect line on the timegrapher!
|dial up||+2 s/d||243°||0.4ms|
|dial down||+28 s/d||231°||0.4ms|
|crown right (12 up)||-30 s/d||190°||0.4ms|
|crown up (3 up)||+20 s/d||202°||0.1ms|
|crown left (6 up)||+19 s/d||200°||0.8ms|
|crown down (9 up)||-32 s/d||195°||1.0ms|
|Number of jewels:||8|
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:||2 hole(s)|
|Functions:||hour, minute, decentral second|
|Size:||10 1/2''' (measured: 23,2mm)|
Flume: 1958 35|