The glass square on the right side of the panel is a mirrored peek-a-boo into the oven so you can monitor baking without opening the door. 

If I were to ever need gas, and O&M would be top of the list.  Lovely range.  

I remember cleaning up several of those ranges for resale. Some of them were filthy. You'd need to take that glass off and use Easy Off to clean it. I can recall several stoves that were so dirty the drip drawers beneath the burners were completely under an inch of grease. Not fun work but at 13 the pay was nice, probably minimum wage but much better than a paper route.