From phillip holmes: "The RCA theater amps had model numbers starting
MI----, meaning, I
assume, "music industry or industrial..."
All of their pro stuff including broadcast used to have MI numbers. I was
told by somebody around 1958 that the letters stood for "master item."
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!