The National Optical brand model 131 microscope is designed to meet or exceed high school teaching requirements, is ruggedly-built, and includes all the standard teaching essentials, plus popular “student-proofing” features. Optical system has DIN widefield 10x eyepiece, locked on, with fully rotatable pointer. Objective lenses are 45mm DIN parfocal, achromatic, color-coded 4x, 10x and 40x giving you magnifications of 40, 100, and 400 power. Built-in illuminator base has a 115V 20 watt bulb, heavy cord and light switch. Has both coarse focus and fine focus knobs. The slip clutch prevents damage to slides and objective lenses. Large 10mm x 120mm stage is acid and reagent resistant. The stage has a built-in condenser lens, and 5 hole disc diaphragm. Stage clips are locked on and spring mounted for ease of use. Overall the microscope is 13 3/4” high; the base is 5”x7 1/2”. Weighs 7 lbs. This is a high quality scope and deserves its popularity.