Halkonite puzzle box
From Tardis Wiki, the free Doctor Who reference
Halkonite puzzle boxes were made from Halkonite steel. They were impenetrable. Nothing could escape them, not even thoughts.
In 2008, Sarah Jane Smith used a box made of Halkonite steel to contain a fragment of the Weserbergland meteorite where the Pied Piper had been trapped. (TV: The Day of the Clown)
Behind the scenes
According to the official SJA website the box is from a place called Halkon.[1]
