Just a little thinking out loud, but have you removed it to see if it has wiring connections on the backside???

Camper Specials had an accessory option for a "camper" wiring harness which may have included a dimmable lighting control switch (???) or even a cab mounted speaker control (???) for radio piped back into the camper compartment.

Since your truck appears to have had the "camper" removed, that may be just a switch that was left to fill a hole in the cab roof when the wiring was removed???

Interested to see what you find by pulling that switch out.

Dan


~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)