Beekers' Revolving Stereoscopes

From the Art Institute of Chicago record

Text printed on reverse of stereocard: Consist in an endless chain, so arranged that each link holds a picture perpendicular, when on the top of the square shaft, by which the chain is suspended. This shaft has a handle on the outer side to bring the pictures successively to view. These instruments have either one pair of best lenses and a window on the opposite side for showing transparent as also opaque pictures. The latter are illuminated by curved reflectors under the top covers. But most of these Stereoscopes have lenses on both sides, so that two persons can see at the same time pictures placed back to back in one holder, thus doubling the capacity. To view transparencies with them one pair of these lenses, fitted in a door moves down to give the requisite light. To adjust the instrument to different eyesights the interior moves to and from by a small handle.