Meiji Techno MA510 - Eyepiece Micrometer (25 mm dia.), 10mm Square into 100 Parts
Microscope micrometers are commonly used for measuring or counting specimens. Eyepiece micrometers, also known as Eyepiece Reticle are small glass discs with markings on them.
The micrometer is mounted in one of the two eyepieces and superimposes an image of the markings over the image of the specimen. Stage micrometers are slides with markings of a known dimension that, when viewed under the microscope, can be used to calibrate eyepiece micrometers. 5mm divided into 100 units, 25mm diameter.