" The ESTEREOGRAFOSCOPIO-VIEWER" apparatus brass hardwood and estereofotos 9 x 18 cm that is both a stereoscope and grafoscopio manufactured around 1900. April 3, 1889 HC White patented his stereoscope exclusive grafoscopio dual function (patent No. 401807). It seems that was produced especially around 1895 -1905 the company sold Sears, Roebuck & Co. in the US mail by H.C. White Company, which sold this model for thousands through intense publicity about the dual role. The basic idea was to bring the entire section of the two images to the center by rotating the prismatic lens, so that two images instead of just one image is visible and can be seen with a magnifying glass as a grafoscopio. Another advantage is that seeing pictures in stereo, high potential errors can be compensated by rotating the prismatic lens. The device can be disassembled for transport.
