Lower Falls of the Ammonoosuc River, New Hampshire
This image is a glass plate used in Magic Lanterns, basically an early slide projector. Despite its small size, just 2 inches square, it has cast its image across many walls and theater screens around the country. This photo was taken around 1890.
Had to scan each half of it, then merge the two pieces together. The emulsion itself was protected by glass plates on either side. Fortunately, the glass plates showed only moderate pitting and small scratches.