Nicko used a 22" Signature Power Ride from around 1990 - 1993 (No Prayer tour thru A Real Live Tour), with an additional 20" Signature Power Ride from 1990 - 1991.
Also I believe by 2006-2007, Nicko was using a prototype of what would become the Signature Reflector Powerslave Bell Ride- you can see it in the Matter of Life And Death "making of" DVD from 2006 and the Download 2007 footage