The GYSI "Simplex" is an "Average Value" instrument, that is, the rotation centers, condylar guides, the incisal guide are fixed to "average" settings. The "Simplex" articulator was the average value version of the GYSI "adaptable", a highly adjustable instrument produced in 1912. Gysi felt compelled to produce this instrument because of competition in the market place and dentist's demands for simplicity. Gysi believed that with the "Simplex" the dentist could provide efficient denture service without the need for "scientific equipment". The "Simplex" would suffice in 80% of the cases.
Gysi suggested that the "protrusive" angle of the "Simplex" incisal guide table could be modified by the use of modeling compound and sheet metal. Apparently, an industrious person modified the lower cast holder to accept a Wadsworth adjustable incisal guide table. It had a horizontal protrusive guide with adjustable lateral wings. This also illustrates the diverse concepts that dentists had regarding the function of the incisal pin and guide.
Dr. Edgar N. Starcke's articles in the Journal of Prosthodontics have more information on the history of articulators.