Hello all. After searching through internet and spare parts documentation till early morning I decided, that the part I needed is (hopefully) 7M3601139C054 (9 square grooves (splines) with center hole). I ordered the part for 25 Euros incl. shipping. That is the price for the code key only, not the bolts for the wheel. As I already have the bolts on the car I think it is a better solution to buy the key onlyfor 25 Euros, instead of the whole set for 45 Euros. I just hope I am right with the part number :-). Even if I am wrong and the key doesn't match I intend to use security torx T60 to unfasten the anti theft bolts. The other solution, proposed by my brother - he was 20 years in the tyre mount and repair industry, is to weld a suitable size nut (M19 maybe) to the anti theft bolt and undo it in this way.