Scrooge doesn't believe the ghost is Marley until Marley removes a bandage. Which bandage does he remove?
The bandage that Jacob Marley removes is one wrapped around his head and chin. The bandage is first referred to as a kerchief, and it's something Scrooge does not pick up on right away. Scrooge grows more and more desperate to convince himself that Marley's ghost is nothing more than the result of bad digestion, eventually dismissing the ghost entirely. In the face of Scrooge's skepticism, Marley's ghost raises "a frightful cry, and shook its chain with such a dismal and appalling noise, that Scrooge held on tight to his chair, to save himself from falling in a swoon." The ghost then unwinds the bandage around his head, "as if it were too warm to wear in-doors." Marley's lower jaw then falls onto his chest, and the horror of seeing such an appalling scene convinces Scrooge that the ghost is indeed real.