The "Z" series (omitted in 1973) was used from January to June 1985.

After ZZZ-999, several letter groups ("words") omitted from 1973-84 were issued.

Here are a few of the ones we know (or suspect) were in this group:
ALE BAG BAT BOX BRP BUB CAN CON COW END FEM FEY FIB FLU FOD FOE FOG FRT GAB GUI HEC
HEN HIP HMO IDO IHS IJU ILL INK INU IVD JAZ JUG KAT KIC KOW RAG RAW RED RUT RYE
HEY (prefix)

Without actual registration documents, it's impossible to tell with 100% certainty which are "word plates" and which are not.
This data is a best guess.

There may have been other plates issued over the years with unused prefixes.
I have a report of the LOW and VEK suffixes being issued to vehicles in 1987 (from Steve Bier).

The new series started at AAA-10A in August 1985 after the initial "word" plates were issued.

This series stopped in November 1992 at HZZ-99Z.