Any Info ona Trio Model SM-109 Multiplex Stereo Signal Generator?

I bought a Trio Model SM-109 Multiplex Stereo Signal Generator at an antique radio swap meet last weekend for $20. The guy selling it said it works but "may need a few adjustments" (unfortunately, not specific).

I could only test it with a mono clock radio and it does put out a signal. Nevertheless, I'd like to have the manual to be sure it's working and calibrated properly.

I looked for information on the unit online, but I can't find anything (also tried looking for "Kenwood").

Does anyone have a manual for it or know where I can find one in case it needs adjustments?