LIVERY 1917-1921 Livery plates with an "L" prefix were issued from 1917 to 1921.
Thanks to the Leib brothers for this info.
1917-1921

1918First plateLeib Brothers
New Jersey Livery License Plate

1920John Anshant
New Jersey Livery License Plate


After 1921, livery plates were issued as a sub-type of omnibus plates.
LATER ISSUES
Livery plates appeared again in 1979 - see this page.