Slide with "L"

For demonstrating image reversal with pinhole cameras, lenses and mirrors as well as with eye models or cameras;
L-shaped aperture, produced photographically on a film, mounted with matt foil between two glass plates in a slide frame
Dimensions of the “L”: 13 x 9 mm
Dimensions: 50 x 50 x 3 mm
Mass: approx. 8 g