Karl Rexer, the german general imprter for GDR watches to West Germany wanted to add a wannabe chronograph to his portfolio around 1970. This watch should only contain two pushers to stop and start the movement, so this would have been more or less a “fake” chronograph.
The engineers of the UMF in Ruhla, who should supply the movements, were not happy with that “fake”, so decided to construct a simple, but efficient chronograph mechanism for the UMF 24, and this was the caliber UMF 24-35 shown here.
The stopwatch mechanism consists only of a center stop second hand, which could be stopped for a short time while pushing the button at 4 o’clock, while it could be reset to zero by pushing the 2 o’clock button. During these actions, the normal movement keeps on ticking, so it qualifies as a true chronograph movement.
The UMF 24-35, here in the version B with fixed hairspring stud, is a simple pin lever movement without jewels, which beats slowly with 18000 A/h. In later versions, the blocking lever was replaced by a plastic version.
This movement was not disassebled, since generally, the long pinions for the center second (stop second) indication are very fragile and additionally, the overall condition of movement and case is very good, and should not be risked to be damaged.
Nickel anular balance|
|Balance bearing / direction hairspring:||Clockwise|
|Adjust mechanism:||Hairspring key|
|Construction type:||pillar construction|
|Winding mechanism:||rocking bar winding system|
|Functions:||hour, minute, decentral second, chronograph, center seconds|
|Production period:||1970 - 1978|
Flume: K3 66|