Originally Posted by
JDNSW
Yes, under the interstate agreement, the states divided the alphabet up for plates in the format ABC-123 some time in the early 1950s (my father in 1953 had ALC-963 in NSW). Qld started with "N", but it was well into the 1960s before they were into the "P"s. I had a car PAD-428 in 1966, but when I moved to Qld and first registered a car there in 1963, it was NRF-912; but all the motor registry paperwork still assumed that numbers were the previous system, using the format Q12345, so I suspect they may have only just adopted the system in 1963. NSW changed first (from AB-123) because they had run out of numbers.