'Collected over the years from books purchased at flea markets, garage sales, used bookstores, etc...'
A strange one, this. Bill Keaggy at Keaggy.com is keeping an archive of pre-owned bookmarks. This is one of a series of projects that occupy Keaggy's time; he has also written the story of his life based on other people's discarded grocery lists (milkeggsvodka.com). Perhaps this is telling.
But let's return to the bookmarks. They range from photographs, cartoons, and newspaper clippings to tickets, receipts, paper towels and notes from dreams. All found in second-hand books purchased over the years. I can relate to this collection, insofar as I once found a passport photograph in a second-hand copy of Kafka's Diaries: a photograph of a complete stranger. I still use it to mark the page whenever I pick the edition off the shelf. Keaggy's site is well worth five minutes of your time, if not more. Click here to see them for yourself.