Gallifreyan Army knife
From Tardis Wiki, the free Doctor Who reference
A Gallifreyan Army knife was a tool issued to the Chancellery Guard. The Doctor had one which was marked as property of Castellan Spandrell.
The Sixth Doctor used his Gallifreyan Army knife to escape from a dungeon on Rigel VII. (PROSE: Players)
The Seventh Doctor used his Gallifreyan Army knife to open a transmat's control panel and later to cut Ace's bonds. (PROSE: Timewyrm: Exodus) During a visit to Gallifrey, he gave it back to Spandrell. (PROSE: Blood Harvest)
