This Swift & son polarized light microscope is either petrological or mineralogical. He belonged to the Department of Geology at Birkbeck College (1907). This institution was previously called the London Mechanics Institute (1823). In this type of microscopes, the circular stage is divided into degrees. The optical tube has a diaphragm and two filters that are introduced with a piston system. It is a robust and complex specimen. It measures 38 cm. Tall