The most popular format for factory produced and home creation was for almost a century was the 45mm x 107mm format stereo image pair.
More economical than the other popular 6cm x 13cm larger sister. Both camera and film did less harm to the piggy bank.
Unis France, makers of all types of stereoscopic viewers, created this once very affordable, practically pocket-sized, nickel plated, folding collapsable, focusing, ground glass diffusor, 45mm x 107mm viewer, ideal for both transparencies and prints (glass or paper
Included with the Unis France viewer is a period (1930s) image of the Carmel, California coast.