The cases for these miniature drum microscopes have a slot on the cover into which the microscopes can be held during use. 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 larger one on the left measures 8.5 cm in height while the smaller one comes in at 7.5 cm.
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 to these microscopes since they have a shape reminiscent of old style furnaces.
