The Fendermen - Mule Skinner Blues (1960)
Two guitarists, one playing a Fender Stratocaster and one playing a Fender Telecaster, both plugged into the same amplifier. This would probably be called "Psychobilly" rock today. Worth a listen just for the title track and their version of "Jack of Diamonds."
"Mule Skinner Blues" by The Fendermen - YouTube