The Junghans caliber 684.12 is a true “Master” (english translation of “Meister”) piece. Construction-wise it is more or less a very little simplified caliber 685, which was the last Junghans chronometer movement.
You can easily spot the relationship to this chronometer movement by its large Glucydur balance, which is beared in the characteristic Junghans shock protection system with their extra large cap jewels and which is here adjusted by a swan-neck regulator. Additionally, the anchor wheel is beared on top in a chaton with cap jewel, secured by a KIF Duofix protection.
The center second and minute hands are driven directly - a very classic construction, and this really interesting: Since the movement nowhere shows signs of a modern construction, it was easily transformable into a true chronometer movement - the caliber 685.
On the dial side, there are no surprises, too: The date advances slowly (while the last part even slips very slow to the following day) and can be corrected in a semi-fast manner by advancing and turning back the crown. And the common yoke winding system shows a decent level of quality.
The caliber 684.12 shown here bases on the simpler caliber 684.00, but contains a date indication, is golden colored and contains a swan neck regulator. The signature “E5” below the balance indicates it production date, may 1965.
|Number of jewels:||17|
Glucydur anular balance|
|Balance bearing / direction hairspring:||Clockwise|
|Adjust mechanism:||Swan neck|
|Winding mechanism:||yoke winding system|
|Setting lever spring:||3 hole(s)|
Flume: K3 -|