For those collectors whom have read my earlier postings by now should be aware that this 4th series of RM50 replacement note that carry the prefix ZB is meant for replacement on those notes that do not carry any 50th anniversary logo i.e. prefix AF onwards.
Only replacement note ZA has 50th anniversary logo on the reserve side of the note. Therefore ZA note is replacement for prefix AA to AE.
RM50 Replacement Note with Prefix ZB