MST 431

MST 431

MST 431


The MST 431 is a ladies' watch movement with a very small diameter. With only 7 lignes (16mm) it hence can be found on the first pages of the movement listing books.

Its execution with 17 Jewels and a rather large anular balance, which is Incabloc shock protected, is up to date for a movement of the early 1960ies, when it was released.

The movement train is constructed counter-clockwise (seen from the the balance), this is a bit unusual, since here the seconds wheel is positioned around 12 o’clock, while on most other movements, it is positioned around 6 o’clock.

Since the specimen in the archive is NOS (New Old Stock), no further teardown was made and the dial was also not removed to avoid damages.

In the lab

The specimen shown here, including its watch, was New Old Stock (NOS), which means, that it was stored for about 55 years. Therefor its oil condition is pretty bad, which you can see on the low amplitude values.
Nevertheless, the deviation values are very well, the maximum deviation over all positions is only 30 seconds per day!

It is not hard to imagine, how well this movement might perform after a revision with an oil change.

Timegrapher result

horizontal positions
dial up +14 s/d 208° 0.4ms
dial down -4 s/d 249° 0.0ms
vertical positions
crown right (12 up) +12 s/d 239° 0.5ms
crown up (3 up) -8 s/d 236° 0.4ms
crown left (6 up) -16 s/d 216° 0.3ms
crown down (9 up) -4 s/d 214° 0.4ms

Technical data

Number of jewels:17
Escapement:Pallet lever
Balance types: Nickel anular balance
Shock protection(s): Incabloc
Balance bearing / direction hairspring:Clockwise
Moveable stud:yes
Adjust mechanism:Hairspring key
  • lever
  • escape wheel, seconds wheel, third wheel, center minute wheel
  • mainspring barrel
Construction type:solid construction
Winding mechanism:yoke winding system
Setting lever spring:4 hole(s)
References: Flume: 1962 -
Inventory number:18029

Usage gallery

Roamer ladies' watch

Roamer ladies' watch