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Osco 850

 

Osco 850Osco 850

Description

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.

base platebase plate

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.

gear traingear train

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.

side view of the gear trainside view of the gear train

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.

RatchetRatchet

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.

empty dial sideempty dial side

On the empty dial side, you can see the yoke winding system.

dial side without date indicationdial side without date indication

The date mechanism consists of a switching wheel with moveable finger. It enables half-speed quickset by turning the time back and forth:

date indication mechanismdate indication mechanism

Normally, you cannot see the date indication mechanism, since it is covered by a plate.

Osco 850 dial sideOsco 850 dial side

 

 

 

 Technical data

ManufacturerOsco
Caliber850
Number of jewels17
EscapementAnchor with pallets
BalanceNickel
Shock protection(s)KIF Trior
Balance cock directionclockwise
Hairspring studmoveable
Regulator typeHairspring key
Movement constructionFork
Escapement wheel, Fourth wheel, Third wheel, Large driving wheel, Center second pinion
Mainspring barrel
Construction typepillar construction
Winding mechanismyoke
Setting lever spring2 holes
FeaturesSCI,QG
FunctionsHour, minute, second, day
Beats per hour18000
Size111/2''' (measured: 25,2 mm)
Image in Flume Werksucher K3 44
Inventory ID 17030
Osco 850OscoOsco85011 1/2''''''Osco 85017 Jewels, 11 1/2'''''', 18000 A/h, SCI,QG
Factsheet

 

 

 

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.

 

 

 

Timegrapher result

vertical positions
positiondeviationbeat error amplitude
12 up  -23 seconds/day  0.0 ms  159 °
3 up  +34 seconds/day  0.0 ms  165 °
6 up  -15 seconds/day  0.8 ms  169 °
9 up  +25 seconds/day  0.9 ms  153 °
horizontal positions
positiondeviationbeat error amplitude
dial down  +50 seconds/day  0.1 ms  199 °
dial oben  -52 seconds/day  0.0 ms  158 °
timegrapher measurings

The timegrapher result indicates, that there's need for a service, especially due to the low amplitudes.

 

 

 

Usage gallery

Prätina gents' watchPrätina gents' watchOsco S gents watchOsco S gents watch

 

 

 

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!