Extracted from the Journal of the Royal Microscopical Society 1886:

Bausch & Lomb Optical Co.'s New Student Microscope. The Bausch & Lomb Optical Co have issued the low-priced microscope shown in fig. 201. It is constructed on the Wale principle of concentric inclination of the arm, by which the instrument becomes more firm the further it is inclined. It also has a new roller motion for the fine adjusment, and a revolving diaphragm fixed to a separate arm so that it can be swung out of the optic axis. The concave mirror is attached to a bar, the axis of which lies in the plane of the stage, so that illumination may be directed on the object from any point below or above the stage. The base and arm are japanned, the latter being fastened at any desired angle by means of  milled heads in the pillars.

Gundlach patent Jan. 21, 1879