Glad you finally got it! It's been a long time coming since it first showed itself.
RE: information, I found that when I was reserving my black plates for the Prince Skyline that they had all the information available there that matched the original owners papers but until that point that they confirmed the plate nonsense they had previously said they didn't have any information.
Government agencies, I guess?
I dare say that they do still have something, mine was A reg and went dead in the 80s and they still had it.