Holmes Stereoscope with ‘Chambre Mobile’ and Stand

The Cham­bre Mobile was an exten­sion for the Holmes-Bates stere­o­scope, designed by the com­pa­ny of Adolphe Block. The exten­sion con­sist­ed of a slid­ing leather bel­lows cov­er that could be fit­ted over the view­ing sec­tion. It con­vert­ed the orig­i­nal­ly open stere­o­scope into a closed sys­tem. The cov­er was pri­mar­i­ly intend­ed for view­ing tis­sue stereoviews.
The Cham­bre Mobile was prob­a­bly sold by Block either with the pur­chase of a stere­o­scope or as an option­al accessory.

(from: Com­pendi­um of Stereoscopes)

Fur­ther read­ing: Block, Adolphe (Com­pendi­um of Stereoscopes)