How to take out mixer cartridge - urgent help needed!

[zaruljica]

How can I take out this cartridge:

Please, please, nobody knows and system is really unusual. What tool should I use and what to do??? Please! Thanks!

 

[Ben-gee]

I would guess that the inner ring will unscrew anti-clockwise, it looks like it needs a special tool but I would try putting an old screwdriver diagonally into one of the square slots and tapping it around with a hammer.
Then the cartridge normally pulls up, need a bit of wiggling sometimes.