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Large Microscope stand Ib by Leitz (Wetzlar), 1893




Leitz Wetzlar research microscope model Ib (1893)

 

This is a first class research microscope, specifically realized for microbiological laboratory work. The year of manufacturing (1893) is clearly identified on the accompanying specification label attached on the inner side of its original dove-tailed mahogany case.

From a structural point of view, it is typical continental model with a solid brass horseshoe foot, bearing the maker's name (Leitz Wetzlar) and serial no. 25385 engraved on the right arm. On the tube it is also engraved the name of the retailer's shop : William Hume, Edinburgh. He had a shop in 1 Lothian street in the 1890's.

 




Advertisement for Hume's shop in 1890

 

Thus, this microscope has been made for export and testifies the presence of Leitz instruments on the market in Scotland already at the end of the XIX century.

The same microscope is listed on the Leitz catalogue of 1894, for the U.S. market, again testifying the diffusion of these instruments also overseas. It is identified as the "Large Microscope stand Ib model".

 




Excerpt from the American edition of Leitz's catalogue of 1894

An identical model has been presented as a gift to Robert Koch to commemorate his discovery of M. tubercolosis and can be seen on display at the Biken History Museum - Osaka University, in Japan.

 




Koch's microscope at the Biken History Museum, Osaka.

 

My microscope is equipped with coarse focus by rack and pinion and fine focusing by a micrometer screw on the milled head. A draw-tube allows further adjustment of the magnification according to the objective used. A double-sided plano-concave mirror provides illumination. Under the stage are present the Abbe's condenser with an iris diaphragm, whose distance from the stage can be varied through a rack and pinion mechanism operated by a screw on the left side of the instrument. The microscope can be inclined at every angle up to 90°C for ease of use, thanks to a hinged joint and a clamping lever to fix it at the desired angle. The iris diaphragm is mounted on a centering apparatus, allowing lateral (i.e. out of axis) movements thanks to a rack and pinion mechanism operated by small screw. This allows a fine adjustment for oblique illumination. The diaphragm is hinged below the condenser, so that it can be moved laterally out of the way when it is not needed.

The microscope is equipped with a triple rotating nosepiece, for fast and easy change of the objectives. The instrument came to me with three eyepieces (I, III and IV as detailed in the catalogue) and two Leitz objectives 3 and 7. I refurbished the instrument by separately acquiring a Leitz oil immersion "diagnostic" objective and a Leitz mechanical stage, both dating c.a. 1900, thus matching the age of the microscope. All the mechanical parts are in perfect order and operating smoothly.

Optically the microscope is excellent, as in Leitz's tradition, giving extremely clear and highly defined images also when tested with the oil immersion objective at 850X.

 


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