Here's why:
* The Gift: The knife is a seemingly simple object, but it carries significant weight. It's a symbol of the convict's kindness to Pip, despite his criminal status. Pip feels conflicted about accepting the gift.
* The Identity of the Benefactor: Pip doesn't know the convict's identity at this point, only that he is a dangerous escaped criminal. The knife becomes a tangible link to a secret that will eventually be revealed.
* The Mysterious Gentleman: Later in the novel, Pip receives a mysterious benefactor who provides him with a great fortune. This benefactor remains unnamed and unknown for a long time. The pocket knife, however, becomes a key clue in figuring out the identity of the benefactor.
* The Revelation: In a dramatic moment, the identity of Pip's benefactor is revealed to be the very same convict who gave him the knife years ago. The knife becomes a symbol of their enduring connection, the secret that has been kept for so long, and the complex relationship between Pip and Magwitch.
The pocket knife, seemingly a simple object, serves as a constant reminder of a mystery that unfolds throughout the novel. It also symbolizes the themes of identity, class, and the unexpected twists of fate that Dickens explores.