What is this switch for?

[eodcoduto]

I picked up this suburban last week for a song and I am getting to it today to see what all needs done. Its an '85 K20 Silverado Diesel, and it has the power rear window but there is another spot for a switch above the window switch. It doesn't have rear A/C so I have no idea what the top one is for. The switch is broken but has two small lights in it. The one on the left lights up when the ignition is on, any help is appreciated!

[eodcoduto]

I found it, it is the rear defroster switch.  The rest of the switch parts were in the console, and the rear glass has been replaced at some point with regular non-defrost glass.