[Stereoscope]

Hugely popular in schools and homes from the 1880s through the 1920s, stereoscopic images were seen with a hand-held stereoscope. By combining two nearly-identical images the experience mimicked a 3-D reality. One guide noted “The making of stereoscopic pictures is one of the most lucrative departments of photography, and the number and variety of subjects everywhere…make a collection of endless extent and beauty." Underwood & Underwood produced over 3 million stereocards in 40 years.