I Spy

It's a periscope, I think one might call it. I didn't wait in line to look through this thing as this woman did at a recent World War II reenactment. But I did see these devices on several of the German tanks and armored military vehicles that were at the event. It allowed the driver to see ahead, I presume, without the risk of raising his head above the vehicle top when there was shooting going on.

Done