n.d., Alexander Beckers of New York City patented a stereo-viewer on April 7, 1857. It had a revolving mechanism which allowed multiple views of different types to be inspected sequentially by turning a knob., Stereo viewer, Archives of Modern Conflict OR National Gallery of Canada, LL/12480
n.d. Alexander Beckers of New York City patented a stereo-viewer on April 7, 1857. It had a revolving mechanism which allowed multiple views of different types to be inspected sequentially by turning a knob.
