SoCal Car ****

If I'm not mistaken, that is a 57 or 58 license plate. Been a long time since I saw one of those.
I lived in Orange co from late 66 to end of 75.
Yep. Thru 1955, california plates were a different size and shape. The yellow with black letters came out in 56 (the 56 was stamped into the plate). Stayed that way till 63, when they were changed to yellow letters on black. Somewhere around 71 (?) they changed to blue with yellow letters, and swapped the number and letter position. Black and yellow/yellow black, three letters first, then three numbers, blue /yellow were numbers then letters.
Black on yellow old plates are now allowed again in cali, IF you have a matching pair.