What is this dash rocker switch? 06 Crescendo 8356

[Big Shasta]

06 Gulf Stream Crescendo 8356.

I can't figure out what this lil switch does. It's a spring loaded rocker switch. Doesn't toggle the mileage display to a trip computer or anything, all that is on the CAT computer to the left. Sorry it's not a good pic, I pulled it off the internet.