VH- Registrations

[Bob C]

I know that a new registration system was implemented because the present three letter alphabetic system was supposedly nearing exhaustion and three characters were retained because it would have been hugely expensive for CASA to change their computer systems to four characters - ie VH-AAAZ.

However, I don't understand why there is a plethora of new styles - ie Numeric/alpha/alpha ; VH-8IC, Alpha/numeric/alpha ; VH-X4B, Numeric/numeric/alpa; VH-88T and Alpha/alpha/numeric ; VH-AC6.

And the old three letter alphabetic system is still being used ; VH-FOH.

Surely it would have been easier to just use one style. Am I missing something?