The Osco 850 is one of the latest inhouse movements of the manufactury of Otto Schlund in Schwenningen, Germany. It is build in a pier construction with undecorated plates and a winding system, that runs partially in plastic bearings. It was probably released in the 1960ies.
The base place of the 11 1/2 ligne caliber clearly shows signs of modern and cost-efficient production, especially because of its pillar construction.
The gear train was very modern, since it did not have a center minute wheel. Because of that, the diameters for the balance and mainspring barrel could be increased, which adds to the power reserve and precision.
The indirectly driven center second is driven by a double third wheel.
The modernly shaped ring balance is secured by two KIF Trior systems beats slowly with 18000 A/h. There's already a moveable hairspring stud for reducing the beat error. The frequency can be adjusted at the hairspring key only.
The ratchet is a nice example for perfect functionality but low costs. It only consists of the simply made click and the spring. Both are located beyond the ratchet wheel, only the end blocks it.
On the empty dial side, you can see the yoke winding system.
The date mechanism consists of a switching wheel with moveable finger. It enables half-speed quickset by turning the time back and forth:
Normally, you cannot see the date indication mechanism, since it is covered by a plate.
In the lab
The specimen shown here came in good condition into the lab, only the mainspring was broken and replaced. No cleaning or service was made.
The timegrapher result indicates, that there's need for a service, especially due to the low amplitudes.
This movement including the Prätina watch is a kind donation of U.Bohnet-Ströbel. Thank you very much for the support of the movement archive!