What is missing in my vent?

Let me start by saying, when you think you took enough pictures of how things go back together, go back and take at least ten more. With that said I need help figuring out what I'm missing in my vent. We decided to go with the original because it was in good working condition and just needed some Mother's mag to make it sparkle again. It's back in, installed, and sealed. And...missing whatever goes in this hole! I took great care in making sure everything was labeled or photographed to avoid an important component like this but apparently missed this. Whatever goes in the hole must be some sort of screw, gear, or something to catch the gear inside so when you turn the handle the arm makes the vent cover go up and down. Does anyone have a photo of this area that might be able to help me? Replacing with a whole new vent is just not an option at this point. Thanks so much for the help in advance.


Vent picture: