Today at the Nauvoo Temple Model, second story assembly hall AND Mezzanine. I am going to redo the seating up here. There is reason to believe that while it was usable, and often used for community meetings on account of it being a slightly larger space, it was not well finished like the lower story.
There is also some indication that the mezzanine level was not finished at all. I found reference to a statement that the lower mezzanine had been finished in anticipation of doing ordinance work. The ordinance work was eventually done in the attic on account of the greater space available. There are further references that the upper mezzanine may not have been finished at all.
From an educational standpoint, both of those changes allow me to easier point out that it is a different level all together.