Mystic chips - Color coins

This is a classic, but still very strong and incomprehensible.

On the table is a beautiful brass box and surrounding it are 5 brass chips. Each sheet has a different color.
The magician turns around and the spectator can do one of the chips in the box and turn off the lid.
The remaining 4 chips he stops away and are thus out of sight.

Then the magician turns back. He could not possibly have seen or what color the viewer has done in the case.
And yet ... the magician knows EXACTLY what color chip is in the box!

It seems like you possess supernatural powers, but in reality, you use a beautifully made gimmick that 100% accurate tells what color there is in the box.
Spectators may examine EVERYTHING there is absolutely nothing to discover. You can absolutely NOT look through the box (it is made of brass).

A classic, but still a good trick!