This is a 68 factory Multiplex setup
Yours looks like an 8 track (Tough to tell with a photo of the back of it.). As I said there is a multiplex 8 track unit that is visually the same as a regular 8 track, except for an extra wiring harness. The knobs on the 8 track controlled the multiplex units tone and balance, as well as the 8 tracks output.