The Doctor's notebook
From Tardis Wiki, the free Doctor Who reference
The First Doctor never went anywhere without his notebook, at least according to his granddaughter Susan. However, he dropped it when he was ambushed by Kal. (TV: "The Cave of Skulls" [+]Part of An Unearthly Child, Loading...{"namedep":"The Cave of Skulls (2)","1":"An Unearthly Child (TV story)"})