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.

1979Leib Brothers
New Jersey In Transit Empty License Plate

1982/84
New Jersey In Transit Empty License Plate

1979 BASEZE-10 ? - ZL-99 ?

1985
New Jersey In Transit Empty License Plate

1990
New Jersey In Transit Empty License Plate


I have also seen ZG-50 on the blue base (on the road), but no picture.
1992 BASEZM-10 ? - Late Z series

2001
New Jersey In Transit Empty License Plate

2003/05/06Jeff Fazekas
New Jersey In Transit Empty License Plate

2004
New Jersey In Transit Empty License Plate


This is the actual "tank" in tow (with plate number ZV-53).
AVERY BASE
3M2 BASE
Late Z series
10-ZA - ?

2009Jeff Fazekas
New Jersey In Transit Empty License Plate



Avery "03" hologram verified on ZY-33.

2010flickr
New Jersey In Transit Empty License Plate

2010Jeff Fazekas
New Jersey In Transit Empty License Plate

c.2010Paul Rosenberg
New Jersey In Transit Empty License Plate

FLAT BASE10-ZG ? -

2017
New Jersey In Transit Empty License Plate