Ok, thanks, it works. I have removed it with a small rubber hammer.
It was a bit rusty.

The System isn't really bad, only very expensive. If I see it right, its 4 times the price of a BT30 toolholder. If one have a lathe, then he can turn the taper to 10° from a BT30, who have the same max Diametre. After that, it needs the recess for the clampballs.