IN TRANSIT EMPTY
These plates are used on "tanks".
See the picture below - and notice the round hatch on the back of the tank. These tanks are used for liquid storage, and when they're in tow, and presumably empty, they get "In Transit Empty" plates.
1977 BASEZA-10 ? - ZD-99 ?
Presumably these started at ZA-10.
1979 BASEZE-10 ? - ZL-99 ?
I have also seen ZG-50 on the blue base (on the road), but no picture.
1992 BASEZM-10 ? - Late Z series
This is the actual "tank" in tow (with plate number ZV-53).
3M2 BASELate Z series
10-ZA - ?
Avery "03" hologram verified on ZY-33.
FLAT BASE10-ZG ? -