What is this dash switch/button?

[dcasalena]

PO (or PPO or PPPO, etc.) hacked my truck up good. New wiring harness is here and ready to go in when it warms up enough outside. Then I might get things back to normal with working lights, signals, gauges, etc. But can anyone identify this switch/button on my dash, it's a soft rubber bubble button? The wiper switch was relocated to the choke hole on the right side of the dash and this thing sits in the original wiper hole. It's so far up in the dash I haven't tried to follow the backside (or even know if it's plugged into anything in the birdsnest of wire, tape, wirenuts, and bubblegum in there).