In 1887, Eugène Gas­ton Clé­ment and Georges Arthur Gilmer joined forces with the opti­cian A. Lav­erne for three years, at the end of which they took over the com­mer­cial busi­ness locat­ed at 10 Rue de Malte in Paris. From 1890 onward, the part­ner­ship Clé­ment & Gilmer offered pro­jec­tion equip­ment and acces­sories for pho­tog­ra­phy, then for cin­e­ma around 1896, and began pro­duc­ing stereo­scop­ic equip­ment around 1900. In 1905, they reg­is­tered the trade­mark Clégil (No. 091.004 of July 8, 1905) for all opti­cal instru­ments. In 1907, Clé­ment and Gilmer part­ed ways and cre­at­ed two sep­a­rate com­pa­nies: Clé­ment E.G. and Gilmer & Cie.
The ambi­tion of Clé­ment & Gilmer was to offer a uni­ver­sal stere­o­scope com­pat­i­ble with the for­mats of the peri­od: 45x107mm, 6x13cm, and the old­er 8.5x17cm for­mat, whether mount­ed on card­board or glass. To achieve this, adjustable inter­pupil­lary spac­ing was essen­tial, as was an adjustable focus­ing mech­a­nism. For trav­el, a fold­ing mod­el was par­tic­u­lar­ly desirable.
The Clégil stere­o­scope appeared around 1905. Its inven­tor was Émile Rosen­gard, who filed patent FR340,444 on Feb­ru­ary 15, 1904.
(from: Moulin­ier et al. His­toires de vision­neuses stéréo­scopiques français­es. Limo­ges, 2025, p. 53. Author’s translation.)

The stere­o­scope shown here bears the ini­tials E.R. Rosen­gard thus also mar­ket­ed his design under his own name. It seems most like­ly that he began doing so after Clé­ment and Gilmer dis­solved their part­ner­ship. After all, this hap­pened just two years after Rosengard’s patent was granted.