It's only impossible if you stop to think about it

Gimli, a dwarf who has lost most of his people’s cultural artefacts: ... I’m sorry Bilbo was given what and did what with it

Frodo, secretly wearing Bilbo’s mithril mail at that very moment but only after nearly 70 years of it sitting in the Useless Dumb Artefacts Museum gathering dust because Bilbo had no idea his cool shirt was worth approximately the net value of their entire country:

Slides were used to teach history of art and architecture since around 1880s until they were replaced by digital modes such as PowerPoint. Since the founding of the Fogg Art Museum in 1895, the Fine Arts Library has served the needs of teaching faculty, art museum staff, undergraduate and graduate students, researchers, and historians at Harvard and around the world. By 1920s, many universities had slide libraries, including Harvard. Since then, over the decades, FAL has acquired over 600,000 slides, mainly from the courses taught by Harvard faculty for teaching.

In the past couple years, the Fine Arts Library’s Digital Images and Slides Collection has been engaged in a large-scale move of our 35 mm slides to off-site storage at the Harvard Depository. 

This collection of over 600,000 slides documents the history of world art and architecture up to the early 2000s. Access for retrieval of items needed by future researchers is being provided through creating HOLLIS records. We have digitized most of the slides, but the archiving of this significant teaching format, nearly in its original arrangement, will serve as a valuable record both of the past art historical interests of faculty and students, and as a tangible reminder of bygone classroom teaching practices.

Edit: Since this very unexpectedly blew up and it was formerly undescribed, a description has been added under the cut!