Box sliding stereoscopes

The box slid­ing mech­a­nism is a focus­ing sys­tem in which the entire front sec­tion car­ry­ing the eye­pieces slides for­ward and back­ward, rather than extend­ing indi­vid­ual eye­piece tubes. The stere­o­scope body is con­struct­ed like two nest­ed box­es, with the front sec­tion slid­ing with­in the rear hous­ing. This design was the stan­dard for many ear­ly stere­o­scopes and remained in use into the twen­ti­eth cen­tu­ry, for exam­ple in mod­els pro­duced by Planox. This sec­tion fea­tures stere­o­scopes using the box slid­ing focus­ing mechanism.