Lucas 54212006 or 8 final?

Hi all.
Please, i have this Lucas rotor 54212006 (may be 8 final number instead of 6?).
I cannot recognize where it was mounted.
Who knows?
Thank you.
Piero

Its a 6, same number on my 74 850, believe its the later rotor thats less prone to loosing the magnets.

Lucas rotor 54212006 is listed in the 1973 Norton Commando Parts Book and also in the 1974 Parts Book Supplement.

Lucas rotor part number 5420144 was introduced sometime in 1974. This rotor is basically a part number 54212006 that has had both of it's faces machined flat so that it can be sandwiched between two large Bellevue washers. These washers disperse the shock loads across the faces of the rotor which would help reduce the magnets from loosening.

Peter Joe