This image was created for a flyer .
The viewer initially see the image of the closed strongbox .
When he opens a leaf of paper that simulates the door
then it's shown the inner of the strongbox empty.
The job required to create the inner of the strongbox as well as the "door"
using the existing texture of the closed door from the original picture.
In order to predict the exact direction of the shadow casted
inside the box a 3D image was rendered as reference.