Max Gray was an importer of Japanese brass models (Akane and Tenshodo) in the late 1940's and early '50's, primarily O scale. Sorry, I can't help with the question of quality because I have never purchased any brass; however, the motors in those days were not very good.
Note that the name was spelled Max Gray, not Grey. A Google search indicates that Max Gray died in the mid-1950's, after which he was inducted into the O-scale Hall of Fame, so the products he imported must have had a good reputation at the time.
Repair parts would be extremely difficult to find today.
