This microscope was invented by Michel-Ferdinand d'Albert d'Ailly, Duc de Chaulnes. The optics were not particularly innovative by comparison with contemporary microscopes. The most interesting feature is the set of three micrometers with graduated disks. Two of the micrometers are fixed to the stage at right angles to each other. They allow a precision movement of the specimen under observation. The third is an eyepiece micrometer mounted crosswise on the tube. The microscope, originally equipped with numerous accessories, is similar to those installed on the dividing engines also invented by de Chaulnes. This instrument was minutely described by the inventor in the small volume Description d'un microscope et de différents micromètres destinés à mesurer des parties circulaires ou droites avec la plus grande précision (Paris, 1768).