SL-1 Aerial Stereoscope Lorgnette | СТЕРЕОСКОП ЛОРНЕТ (СЛ-1)

Russia, 1930s

This lorgnette stereoscope was used by the Red Army NKVD for decoding 18x18-format aerial photographs. The sheet inside the viewer’s padded case contains diagrams and instructions for use:

“Supporting the handle of the stereoscope with your left hand, pressing it tightly to your eyes, look through the lenses at two paired photographs. In this case, two images of each photograph are seen. Then, with the right hand, slightly move one of the images until the two middle images are aligned.”