Pieces of the Scaffold?

[Hess1865]

I heard that when people would write Herndon if he had any Lincoln signatures lying around, Billy would grab a pair of scissors, cut Abe's autograph off a letter or document and send it out!
If this is true, I'd like to know what documents Herndon was using.
What a terrible historical loss it would be if he just tossed them after just cutting off Lincoln's signature.....