Stereoview Cards became popular in the early 1900s. It was an early attempt to create 3-dimensional photographs. A stereoscope viewer was used to view two side-by-side photos mounted on a card. Viewing an image in this fashion gave the illusion of depth. To keep your stereoview card collection safe, store them in our acid-free poly sleeves. We carry them in three different materials: Polyethylene, Polypropylene, and Polyester. For poly material specifications click here. Our stereoview storage boxes are made from 60 pt. Acid-free, Lignin-free, Buffered Board.