Noun
An optical instrument for giving to pictures the appearance of solid forms, as seen in nature. It combines in one, through a bending of the rays of light, two pictures, taken for the purpose from points of view a little way apart. It is furnished with two eyeglasses, and by refraction or reflection the pictures are superimposed, so as to appear as one to the observer.
Source: Webster's dictionaryThe book is an annotated collection of stereoscopic photographs taken by the Victorian era photographer T. R. Williams and it is sold with a focussing stereoscope. Source: Internet
Piper and Carter He called it the "lenticular stereoscope", which was the first portable, 3D viewing device. Source: Internet
Under the stereoscope, the image of the body would seem to float slightly above the background of stars. Source: Internet