Dr Marian Bisanz-Pracken has kindly confirmed the authenticity of this work, which will be included in the forthcoming addition to the Klimt catalogue raisonné.
This drawing is a rediscovered variation of number 1808 in A. Strobl, Gustav Klimt. Die Zeichnungen, 1904-1912, vol. II, Salzburg, 1982 (illustrated p. 181). Drawn in 1907-1908, it is one of the preparatories studies for The Kiss, for the Stoclet Frieze.