Cokin adapter for Hasselblad

I have a 'blad 503CW with the CFE 2.8/80 lens and I would like to get an
adapter for the P series Cokin filters. I think what I need is the "Cokin
Series P Hasselblad B60 Adapter Ring". Can anyone verify that?

And on a somewhat related topic where does the "B60" designation come from
for the Hasselblad lenses, I measured the bayonet diameter on the 2.8/80
lens and it is something like 64 mm or so depending on where you measure at.
Is this just some kind of "nominal" size?

Thanks!