Question: I can not get the shutter of the Schneider Kreuznach 135/3.5 Xenotar to open.
I tried to explain what I know in this picutre:
![image](https://i.imgur.com/6hnafsOh.jpg)

Anyone any idea?
I'm afraid I don't have a manual for the lens and haven't found one online.

Answer: 
Your shutter is a Linhof-branded Synchro Compur. (Only the bezel part is Linhof.) It appears from the picture you posted to have a press focus (the little square tab/button thing near the shutter speed indicator); that button will open the shutter for focus after the shutter has been cocked, and will close if you re-cock the shutter.

(Note: not all Compurs have the press open function.)
Finally. "user47638" was basically right:

![image](https://i.imgur.com/UyBfVhH.jpg)