Maybe the plate of a metallographic microscope

It seems to be the plate of a metallographic microscope that was invented by Henry Le Chatalier (1850-1936), it consists of a light source, a flat glass or reflection prism, an eyepiece, a lens and a plate that is where they are placed the samples to analyze. The samples are analyzed with this equipment, its metal or alloy structure, so they must be very small and flat.