Balcony Box 4 at Chicago Theatre - RateYourSeats.com
What's this called? They're theatre boxes of a sort you can access from backstage. I went to an opera house/theatre. The tour guide didn't mention the material, but they're on the stage.
Theatre Boxes | Oakland Arena
The Benefits of Having a Black Box Theatre - StageRight Performance
Boxes Of Italian Antique Theater Photograph by Naphtalina - Fine Art America