This articulator has two pivotal points. The lower pivotal point represents the opening and closing axis of the glenoid fossa. The upper pivotal point was claimed to be located in the vicinity of the occipital protuberance and provides a lateral rotational center. This design is based on Hall’s “Conical” theory, an arbitrary geometric theory inspired by Monson’s “Spherical” theory of 1898. The vortex of the cone is at the upper pivotal point and the occlusal surfaces of the maxillary teeth are set to be coincident with a segment of an arc of the inner surface of an 8-inch cone. The lateral wings of the incisal guide table for the incisal pin are 45 degrees to the horizontal plane. This is the “generating angle” of the cone. A mounting jig (not shown) was designed by Hall for orienting the casts to the articulator at the level of the lower pivotal point. He claimed it eliminated the need to use a face-bow.
Dr. Edgar N. Starcke's articles in the Journal of Prosthodontics have more information on the history of articulators.