IWC 1871: How to open the case?

[Hoe]

Dear Watchmakers

I purchased an IWC Ref. 1871. It seems to be a true project I am looking forward to work on.

But the first and probably major problem for me is to open the case. It is a square case body that has cut outs in the corners of the back. Each corner has a tiny bore, too.

I did my homework and searched for information online and found a discussion on the Omega forum about the same topic with some hints but with no real result for me. Hints: the case is the same as the one on the “Zenith Respirator”, it works with spring-loaded pins, URL:

https://omegaforums.net/threads/iwc-case-problem-how-to-open-help-needed.16751/

On a website of a dealer I found an image of an opened Zenith case. I can see bolts on the sides of the inner part of the case that contains the movement, URL:

https://www.vtgwatch.com/zenith-respirator-luxe-automatic-28800-date-vintage-watch-vtgwatch.html

Does anyone have some experience?

Best

[clockboy]

This is not the calibur but I would say this is how the movement is assembled into the case.

 

https://watchguy.co.uk/restoration-zenith-respirator-kennedy-calibre-2542-pc/

 

 

[Hoe]

Thanks, I have found that website as well, but the writer does not explain, how he opened the case.

He did not answer the same question that was also asked by a website visitor in 2018 (see comments below the service walk through presentation).

[Hoe]

I am getting closer to this secret:

https://www.poshtime.com/3025.010/Zenith-Respirator-c.1970.php

https://www.catawiki.com/en/l/9923385-zenith-respirator-kennedy-automatic-men-s-watch-square-case-1960s#&gid=1&pid=7

It seems that there are indeed spring-loaded pins holding the case together...

[clockboy]

This is where it is levered I would say. Gently try it with a couple of screwdrivers either end. These recessed parts of the case have been put there for a reason. However be careful because if the dial is tight or has a overhang it will be easy to damage.

 

 

[Hoe]

I managed to open the case with tips from IWC specialists.

In short:

You have to push on the crystal to separate the case back containing the movement from the upper case.

In detail:

You do not need to push the pins back with screwdrivers. There is not enough space anyway, you need a lot of force and you end up damaging the case and the screwdriver. Furthermore, you will somehow push the case together instead of apart.

Expecting that everything will stick together since the last service is ages ago, I put a tiny amount of WD40 into the holes of the spring-loaded pins (see photo above), the space between the case parts and the slot between the crystal and the upper case. I let it soak for some time. Do not use too much WD40… this is watch making here.

Place the watch on its lugs on support blocks (e.g. wood blocks) to generate clearance for the case back to come out.

With your thumbs push gently on one side of the crystal at six or twelve o’clock roughly where the pins are located. Push on the stiffer crystal edge and not on the centre to avoid crystal damage. I could not find a potential replacement for the crystal so far.

The pins are chamfered and will be pushed back automatically from the force applied until the case back is separated from the other case part.

The watch has a split stem. To remove the movement from the case back, first remove the split stem with the crown.

I guess this workflow is the same for the case of the Zenith Respirator.

Happy watch opening!

[nickelsilver]

That's awesome, thanks for the update and detailed description! I work on lots of vintage high end Swiss stuff and haven't run across this case. Big fan of IWC too.

[Nucejoe]

This case looks and opens exact same as my King Seiko.

[rodabod]

I once had a Seiko with those pins in the case. I’m not surprised that design was phased out as it’s a bit of a faff. 

[Hoe]

Small correction to my technical drawing of section cut above:

The rubber gasket goes around the dial and is not placed between the crystal and dial as in my sketch. The previous watchmaker did a bad job by squeezing the gasket between the crystal and dial. This left black stains on it…

[Hoe]

Here it is now.