George Groves is the sound engineer pictured.
http://www.georgegroves.org.uk/index.html
Oral history of Mr. Groves from 1968.
https://archive.org/stream/georgegrovesoral00grov#page/n5/mode/2up
My Nagra:
Story: It was owned by Jose Ferrer and Armin Steiner when they had a "garage studio" in Hollywood.
http://www.imdb.com/name/nm0001207/?ref_=fn_al_nm_1
http://www.imdb.com/name/nm0825897/
You can use an pencil eraser to remove the discoloration you're talking about. BTW, the carbon dust build up on the commutator is usually ok, it actually provides some lubrication and can quiet noisey brushes.
Mike
Yes, I also remember Lee as a very nice man, and I am glad I knew him.
I believe he had a company called Lee Motion Pictures.
Rest in peace Lee.
Mike Riner
I am very sad to hear of Kevin Ward's passing. His humor and sharpness was very apparent and appreciated while he was at ASC. I truly feel our industry just lost someone special. I had a great time working with Kevin at ASC and a lot of good ideas, products and people got there start there.
Mike Riner