K&J Mars Super

Where it’s from

I got this movement from a flea market in Berlin, Germany, for 20 euro. The case back has a “K J” stamp with an arrow going through it, which I believe stands for Kollmar & Jourdan, a Germany-based jewelry company that went out of business in 1977.

What it looked like

This is a small (12mm) ladies’ watch. The case is gold-plated and rectangular, and the dial is square with numeral markers.

The dial has an interesting dent in it near the 11 numeral, that seems to be from something inside the movement.

How I restored it

Oct 26, 2025

I bought this movement for my wife, since she wanted a square movement that had some water resistance. When I saw this one, I had thought it had a gasket in the crown, indicating water resistance, but alas when I opened it, there was not a gasket to be found. Oh well, still a cool piece.

The movement still runs, and not too terribly either.

I’m still recovering from the cold I picked up in Berlin, so I’ll do the movement ID tomorrow morning.

Oct 27, 2025

Well turns out Lens is quite good at IDing movements. I gave it a picture of the movement, and it quickly showed that the movement is an ETA 2410. However, 17jewels shows that that movement had only screwed balances, and was 6 ¾’’’. Measuring this movement, it is 17.47mm, which corresponds to 7 ¾’’’. So, I am fairly confident this is actually the ETA 2512.

Out of the case
The watchmaker’s side
The dial side
First cover plate removed
Motion works removed, with a view of the keyless works
The balance wheel out
A view of the train
The train (mostly) removed
A view of the lovely click
The mainspring

After disassembling the dial side, I think I’ve found the cause of the dent at the 11 numeral: it looks like the screw for the pallet bridge is extending too far out the front of the dial side, which caused it to interfere with the dial. Whoever put the dial back in must have put way too much force on it before realizing the problem, and ended up with the dent. Interestingly, I see two marks from watchmakers in the case back:

Near as I can tell, they say “W570V”, and “WF5/732”. It’s kinda cool that someone cared enough about this movement to actually get it serviced, twice!

Disassembling the movement side, I clearly see the culprit for the dent in the dial: the last person to reassemble the movement mistakenly switched the screw for the balance bridge with the screw for the pallet bridge. The balance bridge screw is much longer than the pallet bridge screw, so when the bridge screw went where the pallet screw is supposed to go, it ended up sticking out way too far into the dial side, which ended up pushing up against the dial. Mystery solved!

Spent the rest of the day disassembling, cleaning, reassembling, and oiling, and I’ve thankfully got it running again:

I think the trace is a tiny bit wavy, but the amplitude is strong enough I’m not too concerned about it. I am especially happy with how well I oiled the cap jewels; I got the perfect amount of oil on both of them, and managed to get the caps on without issue. I’ve had trouble in the past with getting too much oil, and/or sliding the cap stones off the setting and needing to start over. Here, I got them both pretty much perfect on the first try. Maybe I’m getting better?

Feb 7, 2026 12:56 PM

Small update on this: the crystal popped out, but it just so happened that I had ordered some crystal glue (which I didn’t actually use on this). I used some on this watch, and it seems to be good. Hopefully it won’t happen again!