In the Brew­ster-type stere­o­scope by Mur­ray & Heath, the lens hold­er with lens­es can be slid out of the instru­ment for clean­ing. The focus­ing knob is locat­ed under­neath the body. The view­er was also avail­able mount­ed on a stand.
In 1858, Mur­ray & Heath reg­is­tered the use of a reflec­tive foil on the inside of the hinged lid to illu­mi­nate stere­oviews with inci­dent light. How­ev­er, the com­pa­ny was not the first to do so, as one year ear­li­er Paul Émile Chap­puis had patent­ed the use of a mir­ror for this pur­pose, which would ulti­mate­ly become a standard.

(from: Com­pendi­um of Stereoscopes)