Looking for information on this mystery pedal / footswitch. These photos are of a band performing live in 1969. The amps they are using are Magnatone Solidstate M35's. It appears they attached these mystery pedals to the head unit. I'm guessing they are some kind of tone boosters but I have not been able to find similar looking units with the input / output jacks located on top. The configuration appear to be two control knobs over input / output jacks over a single foot switch. Anyone know what this could be? Thanks!