This articulator was designed according to Monson's "Spherical Theory of Mandibular Movement." It was based on the concept that the mandibular teeth move over the occlusal surfaces of the maxillary teeth, as over the external surface of a segment of an 8-inch sphere, and that the radius (or common center) is located in the region of the crista galli. Dr. Monson was one of the founders of the "Geometric" school of mandibular movement. The theory developed in the late 1890's. The articulator itself was invented c.1918 and was patented in 1923.
Dr. Edgar N. Starcke's articles in the Journal of Prosthodontics have more information on the history of articulators.