Mom found this old picture frame years ago and had it made into a SHADOW BOX.
Four pieces of plywood were attached to the back and then to the frame.
Four strips of wood were attached to the inside,
of the outer edge, of the "box" to hold the shelves.
Two boards were cut to fit inside the "box" and made the shelves.
I never figured out why she didn't paint the inside of the Shadow Box.
This would be a fairly easy project if you had scraps of wood and a frame.
The Shadow Boxes of my youth had mirror in the back to reflect the objects inside.
You will need to find them in Antique Stores!