When students reopen school books this month, any number of mysterious items from last year’s class could fall out: a secret love note, a hidden crib sheet, a misplaced retainer. But chances are none will be as intriguing as the ephemera found by Colorado booksellers while flipping through vintage volumes—some with backstories just as gripping as any great work of literature.

Return To Sender

David Satin of Hooked On Books in Colorado Springs was shocked when a pristine WWII Romanian Army medal tumbled out of a book. He wasn’t nearly as surprised, however, as the descendants of the honoree were when Satin tracked them down to return the heirloom, which they didn’t know was missing.

Climb Every Mountain

In the 1970s, scaling 19,341-foot Mt. Kilimanjaro earned you a crisp certificate of completion, one of which fluttered out of a book and into the hands of Linda Dillie, former owner of the Bookworm in Boulder. We at least know who it didn’t belong to: No Coloradan would misplace such bragging rights.

Dated Defense

Storing contraceptives in foil hasn’t always been in vogue. Denver’s Printed Page Bookshop co-owner Dan Danbom discovered as much when he found two envelopes designed to hold 12 loose condoms each. The antique script and artwork on the packaging helped him date it to the 1930s.

Forbidden Scribbles

WWII service personnel were discouraged from journaling; in enemy hands, their musings could reveal valuable intelligence. Not everyone complied, as Danbom learned when he found an American combat pilot’s diary detailing flights in Morocco, Italy, Austria, and Germany between 1943 and 1944.

Rich History

The oil market wasn’t the only thing John D. Rockefeller wanted to control. Wedged inside a biography of the tycoon, Allen Dillie, co-owner of the Bookworm, discovered detailed correspondence between the author and Rockefeller, who had some suggestions for improving the text of a previous draft.