What is the timer in the glovebox for?

[864Lightning]

During some of my trips to the boneyard scrounging for parts. I have run across a couple of late 70's mercedes with what looks like a timer in the glovebox. The only search result I found mentioned a aux heater to prewarm the car.

One was a 116 350se with a locked trunk,,, this car is missing its right tail light, any tips for opening the trunk thru this tail light opening? This would have been a nice car in its prime.. Heated seats, rear head rests, its a shame to see it the way it is now.