AFTER A DESIGN BY JOSEF HOFFMANN FOR THE PURKERSDORF SANITORIUM 1904, MANUFACTURED BY J. & J. KOHN, MODEL 322F, CIRCA 1905

It is quite possible that this armchair was specifically Hoffmann's design and not merely a commerical variation by Kohn of Hoffmann's Purkersdorf side chair. There is a precedent for Hoffmann himself developing a side-chair into a seat with arms: he is credited as the designer of a two-seat bench with arms (shown at the Kunstschau, Vienna in 1908), which was a development of his 1906 design for a side chair, (which in turn was offered as a single armchair variant in the Kohn catalogue of that same year, model no. 371F).
Cf: Ostergard (ed.), exh. cat. no. 54, p. 255, the relationship between the Kunstschau bench and its sidechair and armchair variants discussed.