Determining my original License Plate Number - HOW?

So in the process of restoring my 1960 V200 Valiant wagon. Many steps still to go, but I've come upon this one right now.

When I bought the wagon, it came with one 'original' 1963 CA series black and yellow plate: black background, yellow numbers. I have the original pink slip showing the previous owner's name and the plate number. Goody gumdrops. Under CA license law, I can re-register using this plate as an original YOM plate registration.

BUT, here's my deal:

My wagon is a 1960. It would have originally come with a CA 1956 series Yellow background, Black number plate. I do not have this plate, nor any information on it.

HOW can I find out what the original plate number of the car was? Has anyone tried to obtain an original license plate number by doing a VIN search?

Please advise if you know anything that could help. I am wondering if this would be a lot more work than it's worth, considering I have a 1963 series plate with pinkslip. I probably could even just find a 1956 series plate and as long as the DMV says it hasn't been registered in the last 10 years, I could use that. BUT the thought of the ORIGINAL plate number on the car strikes me as very cool.

Thoughts?