In the 1950ies, the UMF had the problem, that their standard caliber, the UMF M54 / Thiel Start, was not really up to date any more and with a diameter of 12 1/2 lignes it was too big for being used in ladies' watches. So, a new movement had to be constructed - the UMF 23.
It was planned, that this movement powers a calibre series with different qualities and functions, even with a selfwinding mechanism. But in fact, only four different types were made, which only differed by the number of bearing rubies for the balance, the construction and bearing of the lever and different seconds indications (center second or decentral sevond).
The UMF 23-32 shown here is the ruby-less variant with center second.
It was only built for a short period, from 1961 till 1963 and was superseded by the famous UMF 24, which was easier and cost efficient to produce.
The UMF 23 has got a mainspring barrel, which is open on one side. The base plate fully reminds of a conventional pin lever movement.
It has got the classical gear train with (potential) center second at 6 o'clock and directly driven center minute wheel.
The UMF 23-32 uses an indirectly driven center second. The minute wheel is beared by a bent down tab of the bridge, on top there's the center seconds wheel, which is supported by a spring and so prevented from flapping.
Since the successor, the UMF 24, uses a completely different solution, it is likely, that this crude solution was too expensive or too difficult for mass production.
The non shock protected anular balance of this pretty high building movement beats with 18000 A/h and controls a conventional pin lever movement.
Next to the rocking bar winding mechanism, you can see on the dial side the interesting mounting for the ratchet wheel, which is only plugged onto the the mainspring barrel wheel and secured by a flat with two screws. The ratchet is an elaborate construction.
At 9 o'clock there's the balance wheel bearing, which can be adjusted in height. On pin lever movements with a pointed staff, this is the usual way to adjust the bearing.
In the lab
Unfortunately, the specimen shown here is incomplete, parts of the winding mechanism are missing and the hairspring is broken, too. Because of that, no timegrapher measurings were made.
This movement was kindly donated by Günter G. Thank you very much for the support of the movement archive!