Unknown Laco electric

A black dialed stainless-steel Laco electric? Hmm...

The famous Laco electric - it was the first mass-produced and reliable electric watch in Germany of the 1960s - always features a round, golden case (mostly in combination with a golden-white dial). Therefore, this watch that I found in a drawer on a watchmaker market is quite unusual. If you have any info on this one, feel free to comment. I will highly appreciate it =-)

What I find interesting is the poor finishing on the backside of the case. Seems like a prototype construction or a custom made case. The smaller hole was normally sealed with a screw and used for regulating the watch (btw, regulating the Laco electric is somewhat inconvenient as the whole movement has to be taken out on the dial side of the watch - actually a huge disadvantage considering this principally great, accurate movement).

The battery cover was missing. Note the almost unpolished steel inside the battery compartment...

Here a comparison of a standard Laco electric and the black one. I found the lume to contain quite some radium - around 100 counts per sec - guess I´ll better let this one untreated.

Comparing the battery compartments, I found the battery cover of the

standard Laco electric to fit perfectly.

The last pic shows the Laco 861 movement from the non-radioactive Laco - just for those interested...

The movement is pretty simple (there are no transistors whatsoever) but effective, see here for more Laco electric info (Info is just available in German unfortunately). One thing that is noteworthy imo, is the "jumping second" of the Laco 861. I assume it must have been one of the first watch movements with this feature at that time. The underlying mechanism converts three full cycles of the balance wheel into a single "tick". This gives the watch the sound of a mechanical but the looks of a quartz watch. A great piece of horological history, isn´t it?

greetings noq2