The first improvement in the simple hinge articulator was likely a horizontal slot and lock-nut in the upper cast holder to allow for anterior posterior alignment. This articulator appeared in the 1862 SS White Catalogue embodies this feature Chapin A. Harris, 1863, considered it to be one of the best in use but proclaimed that "when plastic is abundant, there is no articulator better than the plastic one".
Harris, Chaplin A.: The principals and practice of dental surgery, 8th Edition, Philadelphia: Lindsay & Blakenston, 1863. JP Article, V.8, No. 3, September 1999, pp. 209-211.
Dr. Edgar N. Starcke's articles in the Journal of Prosthodontics have more information on the history of articulators.