Warranty on UK sales was the responsibility of the manufacturer and some of them transferred purchaser details over to the ledgers but overseas warranties were taken on by the importer.

It's quite rare to find any sort of surviving paperwork from trading companies or dealers. Presumably they simply retained it for as long as was legally required and this sort of thing never survived retirements and closures.

Does the Licensing Department of the State of California or the local districts have an archive ? It'll mean a lot of work but armed with the frame number and his first intial, it may be possible....