Here is the Mirror on its truck. Total height eight feet.

I stretched a gauze over the mirror void but unfortunately the face could still be seen behind this. (Just visible in this photo) So a small curtain was hung in front.

There were lights behind the void to illuminate the Face when it had to appear.
Unfortunately it was only after building this item that I discovered there is silvered gauze sold for just this "mirror" effect.

Below are two photos of the Face with mouth and eyes moved.
(12" ruler for scale)

The changes were made by an operator at the back moving levers and springs.