The lid of the Stealth by Niagara
The hold closest to the wall is for the vacuum assist.
The bottom of the Stealth tank
Rubber seal between tank and bowl
Niagara Stealth Toilet Review with Pictures and Comments
Niagara N7717 Stealth 0.8 GPF toilet
Inside the tank of the Stealth
The trapway of the Stealth
The bowl with water.
Looks a lot like the Briggs Vacuity, which is not recommended. If the Briggs clogged, care had to be taken to avoid forcing sewage into the tank through the vacuum tube when plunging. Did they fix that on the Niagara? Does the Niagara have a jet at the bottom of the bowl?
Quite interesting that someone else decided to take on the vacuum assist flush system. I have a feeling they've learned from all of Briggs' mistakes and got this one right. At least I hope so.