Halford's note

WARNING: Supposition based on limited experience.

You get Halford's Note from Private Halford in the Camp Guardian Caves if:

1. You successfully clear out the caves of Lakelurks, and he gives you the note; 2. He dies, in which case the note may be found on his person (not confirmed).

Based on conversation with Private Halford, the note apparently pertains to the Lakelurk threat in and around Camp Guardian. He wants you to take the note to his (former) NCR superiors and convince them that the threat is real.