Help to take Dorf Handle apart

I have this Dorf faucet start dripping water, the picture of model is attached below.

I try to take the Dorf handle apart so that I can examine the cartridge inside to see whether I need to replace the rubber seal inside. However, I can't figure out how to remove the skin parts, there is no screws, and its surface is too smooth to grib & rotate. I also tried to pull it up without luck.

I have googled and failed to find any useful info. Actually Dorf doesn't seem to be a popular model in US. Please assist, thanks!



Henry

Normally the top ring would be turned to unscrew it. They seldom make provision for using tools so unless it will turn by hand you have to wrap it with tape or rubber before grasping it with a pair of pliers or a wrench. Depending on its age, you may discover there is NO rubber washer and you need to replace the whole stem cartridge.

Dorf is an Australian company. I don't know if this information is current, but my notes show customercentral@dorf.com.au and a California phone number of (800) 634-3903. You probably have a ceramic cartridge that cannot be repaired but must be replaced. A Dorf cartridge is shown at www.plumbingparts.org .