63-72 Calif Comm Black Plate sequence

[19553100]

I've been looking for some correct black commercial plates for my
recently purchased 1967 C10. There seems to be very little
documentation on the internet regarding the correct issuing
sequence for Black Commercial plates in California.
Maybe someone here already knows or has a theory.

I've been doing my own research and here's mine.
There seems to 2 different issuing sequence formats from 1963 to 1972.
I don't think that there is an exact date for the change because it would have been different for each individual DMV Office. I think that as their supplies ran out for the first sequence they would begin issuing the second.

The first sequence in 1963 began with an (A 12 345) format. The issuing sequence determined by the first letter. I think the DMV miscalculated the number of commercial plates that would be issued because this sequence seems to reach the end of the alphabet somewhere in the 66-68 years depending upon the individual DMV Office.

The second sequence began with a (12 345 A) format, with the issuing sequence determined by the last letter. I've seen black commercial plates on 1971 and 1972 trucks that only seem to extend mid-alphabet.

I've been keeping a lookout for for the last few months for local pickups with black plates and the theory seems to play out.

I just purchased a set of (Y 70 584) plates that I think would be correct for my 1967 C10. There is a local nicely restored '67 Longbed with Black plates that start with a V and he believes they are original to the truck.
If you have a California truck with black commercial plates that you know are original to your truck...please let me know the year and plate number to see if we can verify the theory.
Thanks!!