Long time lurker - amazingly helpful forum for fixes, but for once I'm stuck.

I was going to replace the sunroof seal when I noticed that the rear doesn't vent - and I don't remember it ever venting. I'm wondering if a previous owner got sick of it sticking and did the mod. I can't seem to find anything on forcing it open - or anyone else not getting it to open. What have I missed?

 

So following the instructions from a "help! my sunroof is stuck" thread but in reverse, I pushed the sliders towards the front of the car and got the rear glass to "vent." Now to confirm if it's broken or disabled. They didn't seem like they required a huge amount of effort, to move but I could tell it's been a while since they've moved. Maybe just needs a ton of lube?