The Collaborative International Dictionary of English v.0.48:

Stereomonoscope \Ste`re*o*mon"o*scope\, n. [Stereo- + mono- +
   -scope.]
   An instrument with two lenses, by which an image of a single
   picture projected upon a screen of ground glass is made to
   present an appearance of relief, and may be viewed by several
   persons at once.
   [1913 Webster]