Early 1970s GTE (Automatic Electric) KSU hardware was remarkably similar in appearance to ITT, Stromberg-Carlson and Western Electric. It was also electrically-compatible. I'd even go so far to say that the gray fiberglass covers were all made by the same subcontractor. My guess is that your KSU looks like ITT's or Western's 501.

ITT 501 KSU (Floor standing model), without cover


Ed Vaughn, MBSWWYPBX