Various Aperture Discs, Late 19th Century

Ten various types of copper alloy aperture discs. Four of the disc are circular with a circular bar around the outside these are numbered 1-4 with increasing size of central circle. Three of the discs are numbered 5-7 and have rectangular inlets cut out of them, one inlet for no.5, two for no.6 and three for no.7. Two of the remaining discs have a central circle cut out of them one large one small. The final disc has a spoke like aperture. Stored in black Japanned tin box. Microscope Accessory.