Ca Black Plates
Great subject, as a native I have always been a license plate reader. Getting pretty scarce, don't see many on a daily basis anymore. California did it's last complete plate reissue in 1963, so some vehicles have the same plates that could be up to 48 years. Considering they stopped issuing them in late 1969. Here are some of the ones with the year of vehicles that I have owned or family owned, i can't remember all the numbers, so I will give a prefix only
1962 HUB
1964 HKT
1964 OUN (our family purchased this car in mid 64)
1965 MOX
1965 PKH
1967 UJJ
1968 XOS
1969 XCH
1969 ZDY
I have even seen some 1970 cars that must have been sold in late 1969 with Z prefix Black plates It seems to be real hard to figure out exactly whats years/numbers were issued. Some DMV's went through plates quickly, like San Diego or Los Angeles, a small county like Inyokern or Mono may have took years to go through a box. The best way to see whats out there is look at old photos, movies or advertisements. Watch Get Smart or The Beverly Hill Billy's to see what cars had what plates. I have even seen Black California plates on The Andy Griffith Show,which some producer must have missed.
In regards to Commercial Plates, I have seen up to 1972 vehicles with Black plates. Interesting note on the commercial plates, they just changed the color & kept the same sequence, as opposed to cars, they always switched letters to numbers or numbers.
In the mid 70' when personalized plates came out thousands of these were turned back in & don't let anyone tell you, they had Black personalized plates, they started issuing them about 1974.
Now with year of manufacture plates including the Black plates, it will be harder to tell if a car was originally sold in California.
As a note on the Blue & Yellow, my father purchased a 1970 Chevelle Wagon in December 1969 & it was issued Blue Plates 074-AUD & a neighbor purchased one at the same time & received a Black plate with a Z prefix.