I do not know it and I do not think that at this site there are any people who are active audio archeology. The site has a few Hungarian members but I do not think they post. If anything try the Audio Heritage forum.
I am not sure what you are trying to find but they are usually very good to gig out older publication and indentify the things from past. Alternatively if you are in US and the subject is truly valuable to you then get in touch with Bruce Edgar. He in one way or other was observing whatever was out there and he will be able to lead you what you can get further information.The Cat
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche