Made by E. Leitz. London, Berlin & Frankfurt. In the original fitted carrying case with lenses, etc.  Manufacturer’s  No. 112635.

A microscope (from Ancient Greek: μικρός mikrós 'small' and σκοπεῖν skopeîn 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisible to the eye unless aided by a microscope.