I have GE P7 double ovens the same color as the range. Does your range have a window in the door? My ovens do and I can't lock the door until I raise the shield to cover the window. Once this is done then you push and hold the latch release and move the lever to lock to lock the door shut. After that you set the start and stop times. Nothing will happen until you get the stop time set. Once it has gone through the cleaning cycle. it won't let you unlock the door until its cooled down. Also if your lucky enough that your oven racks haven't been run through the cleaning cycle and are still nice and bright I would make sure they come out of the oven before you start.
I will look for the instructions for my ovens and post them if you would like. I haven't looked for them in quite awhile but I know I still have them.
I have double wall ovens from 1970 with the P7 cleaning. In order to get the door locked to clean, you need to raise the shield if your oven has a window. After that press and hold the latch release button while you move the lever to lock. That will allow you to set start and stop times to get the cycle started. You must set the stop time in order to get things going. Once it has finished cleaning you can't unlock the door until its cooled down but after that then push and hold the latch button again and unlock. I remember the instructions saying not to use any type of oven cleaner in an attempt to clean it. I will find the instructions manual and upload it if that would be of help.
That looks completely unused. I would keep that, it's better built than anything you can get today and will still be working after anything sold now has been replaced most likely!