In reply to Phil.

Thanks for the reminder Phil. I think I first came across that piece of Baker's while researching the size of notes/ideas/thoughts in August 2021 and looked at it right after some of Beatrice Webb's work. Luhmann's slips show some of this sort of wear as well, though his show it to extreme as he used thinner paper than the standard index card so some of his slips have incredibly worn/ripped/torn tops more than any grime. Many of my own books show that grime layer on the fore-edge in sections which I've read and re-read.

One of my favorite examples of this sort of wear through use occurs in early manuscripts (usually only religious ones) where readers literally kissed off portions of illuminations when venerating the images in their books. Later illuminators included osculation targets to help prevent these problems. (Cross reference: https://www.researchgate.net/publication/370119878_Touching_Parchment_How_Medieval_Users_Rubbed_Handled_and_Kissed_Their_Manuscripts_Volume_1_Officials_and_Their_Books)