This type of vertical circle reflecting goniometer was invented by Eilhard Mitscherlich (1794-1863); see: Eilhard Mitscherlich. Prince of Prussia chemistry. It is with an instrument of this type that he discovered the concept of isomorphism (crystals of different substances having the same crystalline form; see chapter 12 in the book linked above). The instrument shown here is constructed of brass having both black oxidized and nickel plated surface finishes. The instrument is unsigned by the maker and it likely dates from the late 19th to the early part of the 20th century. This goniometer is very similar in design to those made by the firm Voigt & Hochgesang, Göttingen.