That information would probably be found in court house records in New York, it is not expressed publicly online as far as I know. marshall built the first of his amps based on the chassis of the Fender Bassman and tweaked it especially for guitar and it eveolved from there. There was a lot of controversy over Marshall during the mid 70`s through about the mid 80`s. I was a dealer in the early 70`s and had access to Marshall amps but had to order through the west coast to get them due to rose-morris handling the exporting for jim marshall, and their importer was on the west coast. Jim cut a deal with Korg USA to import and distribute on the east coast out of New york around '74. All of a sudden my Korg catalogs had "exclusive distributor of Marshall Amplification" on them and I then had no trouble getting marshalls. Meawhile, from out west there were still some "Park" amplifiers floating around which were Marshalls with a different faceplate. They disappeared within a couple of years. In the 80`s marshall began handling the exporting themselves, yet Korg was the the authorized importer over here. In the 90`s marshall reintroduced the park line as a lower cost alternative to buying a Marshall. I really don`t know much more since I sold the business in the late 70`s and didnt keep up with the inside stuff anymore.
