Book Ephemera?

In my thirteen years of selling books I have concentrated on learning about the books, the bindings, the authors, etc. I have not paid much attention to the things that have fallen out of the books when I flip through them, determining wear and value.

For example, the above small advertising insert would have ended in the circular file even a couple years ago but I would have spent hours finding out that Gautier had a very broad bibliography, being a prominent writer of the 19th century and that this book, a collection of six short stories, was published late in his life but were saucy and adventurous enough to spawn several vaudeville acts 40 years later on.

Now, having slowed down a bit, I am more interested in the story of these small bits. I've seen many of these small pieces of paper advertising a specific book from a specific publisher. Printed on "regular" paper, often in two colors, I am coming to question their efficacy, history, prominence, etc.

Unfortunately, the provenance of these advertising slips, and the larger bookmarks, seems to me much more difficult to ascertain. Perhaps because I do not know the terminology or where, really, to start.

Do you have any suggestions? Have you seen one of these that was particularly memorable? Comment or send me a note and let me know!