The drum microscope or Martin-type was created by Benjamin Martin in 1738 as the ‘pocket reflecting microscope’. The drum microscope is basically a single tube the user simply slides within an outer cylinder to focus and with a drum-shaped sub-stage that houses a reflecting mirror at the base. Objectives and eyepieces were interchangeable on some models. Some designs in the late 1800s differed by having the outer tube attached to side posts mounted to the drum stage below and adding a focusing rachet knob. In another variation the tube was attached to a rear post. The scope is small, portable, simple, rugged and remained popular throughout the 1800s well into the 1900s. Martin’s early model was one of the first microscopes to use an eyepiece micrometer for measuring the dimension of objects under magnification. ‘Chest microscopes’, intended for the amateur and popular from the late 1700s to the mid-1800s, are small compound microscopes that dismantle for storage in a fitted wood box. The Leitz Minor-5, introduced in 1924, is a small field microscope with a collapsible hinged frame, so the instrument can be folded-up to fit in a leather pouch.