The movement shown here has got no markings at all, but with a little research and a tiny doubt, it can be assigned to the caliber ZSH SS7 of the Shanghai Watch factory in China. It is not 100% sure, since the term “SS7” was used for all kinds of the 17j ZSH movements, regardless whether they use a date indication or not.
This movement is a bit rare, compared to those without date, which were used in countless cheap watches.
The construction is very traditional and easy serviceable - the large four-leg ring balance contains a thick and rugged (hard to break accidentially) hairspring, which is connected to a moveable hairspring stud and whose effective length can be regulated directly on the hairspring key. The balance beats with 21600 A/h and is shock proctected. The shock protection system is made in China and its springs were available in many different shapes, starting from an Incabloc-like type to a “four leaf clover”.
All gears are beared in jewels, even the cannon pinion is jewel-beared on both sides!
On the dial side, you see, whan was above described as “four leaf clover”: The shock protection spring. It reminds a bit of a KIF flector. Otherwise, there are no surprises on the dial, and of course, this movement uses a yoke winding system.
The date mechanism is as simple as genious: The hour wheel drives with six teeth the date wheel with 12 teeth. One of them is longer than the rest and elastic, too. It advances the date ring and is also responsible for the correcting mechanism, which does not turn the date wheel backwards when the time is set back.
As on most of those chinese movements, the top plate was here smeared over with glue to fix the dial. Obviously, dial feet were a luxury item…
|Number of jewels:||17|
Nickel anular balance|
China (different types)|
|Balance bearing / direction hairspring:||Counterclockwise|
|Adjust mechanism:||Hairspring key|
|Winding mechanism:||yoke winding system|
|Setting lever spring:||3 hole(s)|
|Functions:||hour, minute, second, day|
|Size:||11 1/4''' (measured: 25,4mm)|