Instruments of this sort, which projected the image of objects placed on them, came into use in the second half of the nineteenth century. The “J. Duboscq / à Paris / No. 54” inscription on this example refers to Jules Duboscq, an important scientific instrument maker in Paris.
This form came to be known, in the twentieth century, as a viewgraph or an overhead projector.
Ref: J. Duboscq, “Appareil pour la projection des corps placés horizontalement,” Journal de Physique Theorique et Appliquee 5 (1876): 216-218.
Debbie Griggs, “Projection Apparatus for Science in Late Nineteenth Century America,” Rittenhouse 7 (1992): 9-15.
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