Piero
The Atlas and Commando rotor nuts are not the same.
The Commando nut is as described by Thomas to accommodate the wide triplex chain. The rotor is pushed outboard about 3/8 inch (9 mm) because of the wide chain, and the nut acts as a sleeve (per Thomas explanation). The Commando rotor is also different than the Atlas... the rotor bore is larger to accept the sleeve of the rotor nut.
I am not familiar with the P11 rotor and rotor nut. The Atlas rotor nut is like most nuts .... plain.
Ciao
Slick