The design of this wallet is not original, but it belonged to a simple trick in some magician game box of my youth. The working principles are similar to Jacob's Ladder
I drew a simple 3D schematic to show you the way to connect the ribbons which keep the money. Notice that although in the 3D and in the animation you see a space between the two plates, in reality the ribbons are very tense and they keep the plates adjacent.
Here a 3D model ready to explore with Sketchup