John the Revelator

There is an old Negro folk song called "John the Revelator" sung by Odetta that can be heard on Roger McGuinn's "Treasures from the Folk Den."  Hence the title of the collage below which was created using an unusual wooden antique I picked up somewhere. If anyone knows what the piece was originally used for, I would appreciate you letting me know. The panels slide up and down.

John the Revelator (2008) (15" x 8" x 2")