Also note that when I got mine, the 'two stage' action was not working. This was because the spindle assembly had been incorrectly assembled. It was a few years ago now but as I recall:
There should be a Allen-head grub screw somewhere on the circumference of the big knurled knob. Loosen this and unscrew the inner threaded spindle. Clean and lube. You'll see there is a sort of sprung face cam with a step which controls the 'two stage' action. On mine this had been assembled 'locked solid'.
As I recall all it needed was for the knurled ring to be backed off a few turns to provide space for the cam to move, and re-tighten the grub screw.
You'll probably have no problem figuring it out once the spindle is removed (and the first image I posted should also be helpful)
If you have lost all the markings on the two or three-position clamping force adjuster, try wiggling it with the Allen key as you tighten – you should be able to feel the 2 or 3 'flats' where the cam seats in each of the 2/3 positions.
Just in case it's not clear from the German instructions to use the vice there are three stages:
(1) Turn either the knurled knob by hand or use the handle (on the hex spindle). Jaws move 6mm per rev until contact is make with the workpiece.
(2) Turn the handle (on the hex spindle) a little more until it clicks – there is now 3-4 kN pre-tension on the jaws, and the knurled knob stops moving.
(3) now finish turning the handle until it reaches its hard stop (set by the 2 or 3 position cam) so that the full clamp force is applied (takes surprisingly little force). STOP at that point as trying to move the handle further will damage the vice.
Hope that gets you going 
Edited By Bikepete on 10/03/2019 11:10:21