Slides with hole, set of 3

For demonstrating the optical systems in cameras and pinhole cameras and in the model of the eye;
Three pinhole apertures of different diameters, each produced photographically on a film, mounted between two glass plates in slide frames
Hole diameter of the apertures: 1, 3 and 8 mm
Dimensions: 50 x 50 x 3 mm each
Mass: approx. 24 g