That it most certainly aftermarket. You can buy those switches at the parts stores. You're going to have to trace the wires connected to it to see what it powers. Possible an aftermarket sound system was present at one point? Or some custom lighting? You can never tell unless you see what it powers or you follow the wires.
2011 GT Premium 6-Speed
GO:S550 Longblock, Boss 302 Intake Manifold, Boss 302 Exhaust Cams, Airiad CAI, Boss 302 H-Pipe and Side Pipes, Borla S-Type Axlebacks
SHOW:GT350 20” Wheels, California Special/Boss Rear Spoiler, LED Marker Lights, S550 Style Headlights with HIDs