Already in 1923 Thiel released their 18 ligne pocket watch movement, called “Regular”. It was a simple, but in details clever constructed pin lever movement.
During its 67 years of production, the name changed several times, from Thiel Regular to UMF Regular, to UMF M 1 and finally to its ultimative name, UMF 83-31.
Not only the caliber name changed over time, but also the execution, where at the end not only the separate balance cock vanished, but also the lever cock. And in the last version, called F4, the hour wheel became a plastic part.
On the punched base plate, which is brass toned in the older versions till the early 1970ies, you can immideatly see, that it is a simple pillar construction, on which the gear bridge sits on three pillars. Of course, there are no bearing jewels.
The gear train could not be more classical, no wonder, since it originates from the 1920ies: The mainspring barrel (which could be released seperately) drives the center minute wheel, followed by third and fourth weel on which the decentral seconds hand sits. Finally, there’s the escapement wheel.
There’s a little speciality on the lever - probably to increase its operational safety, on its gear side end, there’s an u-shaped form, which sits above the escapement wheel and on extraordinary deflection, it should bump into the axle of the escapement wheel and would so prevent bending the lever pins.
The UMF M1 (83-31) of course has got only a simple screw less anular balance, which runs in two punch bearings, of which the one on the dial side is adjustable in its height. Since this is a very rugged construction, there’s no other shock protections.
Surprisingly, a real ratchet with a true pawl was used and not only a simple click spring. Besides this, this movement has got the expectable rocking bar winding mechanism and large holes for the escapement wheels and the lever, which allows easy service.
At 3 o’clock you see the height-adjustable balance wheel bearing.
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:||18''' (measured: 38,7 / 44,2mm)|
|Production period:||1923 - 1990|
Flume: 1947 92|