Sliding-box focus

With sliding-box focus, the complete lens panel with the oculars slides in and out of the body of the stereoscope.

The earliest known design for a sliding box stereoscope is described in a patent by Gaudin from 1854. The design consists of a lens panel that can be moved by means of a rack-and-pinion mechanism.

Patents and registrations:

Number: 19377
Système de stéréoscope
Filing: 15-04-1854, Applicant(s): Jacques Charles Emmanuel Gaudin. via: archives.inpi.fr