I happened to be watching America Pickers recently and they found the guts of a megalethoscope. Very intriguing, sort of a giant slide viewer.. from very long ago I might add. Had me wondering if anyone had ever seen one in the wild. Also wondered if one could fabricate something similar for large format slides???
http://en.m.wikipedia.org/wiki/Megalethoscope
http://en.m.wikipedia.org/wiki/Megalethoscope