This is a stainless steel replica of the key used to wind up the clockwork tin Zathura "board game" in the movie Zathura.
The key plays a major part in the movie and is passed from player to player whenever someone must take their turn.
This key was modelled in 3D by Zenix from the RPF based on reference images, then 3D printed from stainless steel by ShapeWays.This screencap from the DVD shows how the key appears on screen.
