Note that these two examples have a device for immobilizing the microscopic preparation; there is cylindrical sleeve that slides vertically on the body of the microscope clamping the microscope slide in place. There are variations of this microscope which do not have this clamping device.
Note that these two examples differ slightly in size.
The catalog of the
Billings Microscope Collection of the Medical
Museum of the Armed Forces Institute of Pathology
(Washington, 1974) attributes the manufacture of
these miniature drum type microscopes to the
French maker Bertrand, Paris and dates them at
about 1840. However, it is not at all clear how
this attribution was made or if dating is accurate. It is
possible that this form of microscope was made
over an extended period of time. In fact, a
similar microscope was offered in the 1922
Catalogue Société des Lunetiers as shown
below. Nevertheless, these miniature case-mounted drum microscopes
are now referred to as "Bertrand Furnace Microscopes".
The word "Furnace" was applied because these microscopes
have a shape reminiscent of old style furnaces.