help me id a part

I went to a car show yesterday and saw a really nice 32 highboy (done 60s drag style). When I checked out the interior, I noticed what looked like a square magnifying glass mounted to the windshield towards the top left corner. It was not just a stick on thing.... it was wrapped in a metal frame and bolted in. I did not take a picture and wish I had.... does anyone have an idea on what this is?

 

probably a traffic light viewer

 

Did it look like this?



This is for viewing traffic signals.