Calibration slides, also known as stage micrometers or calibration standards, are precision tools used to calibrate the magnification and measurement accuracy of microscopes. The markings on a calibration slide are manufactured to exact specifications, with divisions of known sizes. When viewed, the markings ensure that the microscope's scale bar, measurement software, or eyepiece reticle provides accurate measurements and position localizations.
This is just another tool, i've implemented for testing purposes...