It is a necklace with an amulet of a smooth black rock. Peeking out from the face of the black rock is a small circular orange stone
When the orange stone is pressed, the wearer sees the last 10 seconds play out before them. During that time people around the wearer just see them stare off into space.
you saw whatever your eyes saw for the last 10 seconds. If you press it twice you see you staring off into space. You can look at different things when you revise.