Chain-Stereoscope ‘à court foyer, chaîne interchangeable’, Short Focus

This Amer­i­can inter­change­able-chain, short-focus stere­o­scope has a dis­tinc­tive con­struc­tion, par­tic­u­lar­ly in its chain mech­a­nism. Unlike ear­li­er mod­els that used wire chains, it employs stamped and cut met­al frames that form a per­fect bor­der around the pho­to­graph­ic image. Since these frames are the same dimen­sions as the stereo­scop­ic views, the dis­tance between the eye­pieces and the image can be reduced, result­ing in greater mag­ni­fi­ca­tion than with oth­er models.
It was made in pol­ished old mahogany or thuya wood. It is equipped with rack-and-pin­ion focus­ing binoc­u­lar lens­es and achro­mat­ic glass lens­es. Adjustable eye spac­ing was avail­able as an option.
(from: Moulin­ier et al. His­toires de vision­neuses stéréo­scopiques français­es. Limo­ges, 2025, p. 113. Author’s translation.)

This stere­o­scope was designed for chains hold­ing 50 views. It was avail­able with either an inter­change­able or a fixed chain. The chain mech­a­nism was patent­ed in July 1902, fol­lowed by a patent for a mag­ic lantern into which the chain could be insert­ed. It remains unclear whether the mag­ic lantern was ever commercialised.