A Brew­ster-type stere­o­scope is a refract­ing hand-held stere­o­scope intro­duced by David Brew­ster in 1849. The device was lat­er devel­oped into a view­er with an enclosed hous­ing. This mod­i­fi­ca­tion occurred large­ly in response to the use of daguerreo­type stere­oviews, which exhib­it­ed high sur­face reflec­tiv­i­ty and there­fore required shield­ing from ambi­ent light. A hinged lid was added to the top of the view­er in order to direct inci­dent light onto the daguerreo­type and, sub­se­quent­ly, onto paper stere­oviews. Jules Duboscq lat­er incor­po­rat­ed a ground glass ele­ment to enable illu­mi­na­tion of glass stere­oviews by trans­mit­ted light.

(from: Com­pendi­um of Stereoscopes)

The illus­trat­ed view­er not only incor­po­rates Claude­t’s patent for larg­er lens­es but also George Cooke’s patent for the use of aux­il­iary lens­es. In this case, neg­a­tive cor­rec­tion lens­es can be swung into posi­tion through brass knobs on the sides of the lens tubes.