you learn something new everyday.

from BibliOdyssey:

Watch-paper Prints

“Originally designed as a simple protective insert, watch-papers came to be used as an advertising medium for the watchmakers in the second half of the 18th century and another means by which print artists could ply their trade. These types of ‘professional’ or conservative watch-papers form the majority of the genre, but a popular ‘amateur’ variety also emerged that were valued as keepsakes.”