After lot more looking I have found that most PP2s I have come across have a centre cane surrounded by two concentric rings, then a 1,1,2,2 formation.
I have found a few, mostly pre 1977 that have the two rings then a 1,2,2 formation.
But I still haven't found one like mine with 3 rings and a 1,2,2 formation !!

Anyone out there got one or a picture to post?
Many thanks,