Here is a word that I have never heard before. Now that I know what it is, it does not surprise me that Sherlock Holmes was examining one in The Greatest Adventures of Sherlock Holmes before he took the case of “The Golden Piece-Nez”.
Palimpsest – a manuscript or piece of writing material on which the original writing has been effaced to make room for later writing but of which traces remain
Usage: “He [was] engaged with a powerful lens deciphering the remains of the original inscription upon a palimpsest.”
I am including an image of a palimpsest from Wikipedia. You can clearly see the different texts in this image.