The drawing below is taken from S. Bradbury (1967), The Evolution of the Microscope, showing a similar microscope as it appears in Johannes Zahn (1702) book Oculus Artificialis Teledioptricus in comparison with the microscope type seen here.
Fruit wood "flea glass" simple microscope, 1680-1750
This is a simple microscope made of fruitwood. It has a single, biconvex lens mounted in an aperture in the top turned wood piece. The lens is maintained in position with a brass circlip and the instrument is contained within a cylindrical pasteboard etui coated by marbled paper. These microscopes appear in several forms. They were apparently produced by “toy makers” in Italy and the German lands to satisfy the curiosity of the common people in natural science. This type of handheld microscope was popular during the late 17th and into the early 18th century. They were made of wood, horn and bone.
The magnification lens is facing a brass sprung pin to which a flower or an insect could be speared for inspection (thus the term "flea glass", an English translation of the Latin name vitrum pulicarium). Focusing was achieved by moving the sprung pin backwards or towards the lens.
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Johann Franz Griendel von Ach und Wankhausen in Micrographia nova Battle Between Flea and Louse 1687