Actually John I think they've been cancelled with either black spray paint or a marker pen which is a shame but they came from an ex security chap so it was probably done in-house so he could have them as opposed to being destroyed. I could be mistaken but that's what it looks like so...........
Glad they didn't do the 2 higher denominations but I suppose the "cash" (non-negotiable) ones had a different rule than the square float (negotiable) plaques although why is anybody's guess. I wish they were bicolour as never seen any before (as you said).