These plates were introduced in 1997 with the CC 0000 AA format as you can see in the picture and
the last two letters mean the country of the plate, as in the new diplomatic plates
(see table). Before 1997 there wasn't any kind of consular plate in Italy and normal or diplomatic plates
were used for this purpose.
You can see the seal of the Italian republic and the oval with I of Italy on the top.
I need to thank Alessandro De Zuani for this good scan: nice to have met you in Rome!