I just found a very similar work by the same artist (also posted here on Curiator). Note especially the position of the right hand is different, varies between the two works. So far, I've not been able to ascertain which is which, but apparently as indicated on the German Wikipedia page, one is a study for the other, which is the final work: Venus in der Grotte – Studie (Wien, Leopold-Museum, Inv. Nr. 583), 1914/15, Öl auf Leinwand, 75,5 x 62,7 cm Venus in der Grotte (Wien, Leopold Museum, Inv. Nr. 1999), Öl auf Leinwand (https://de.wikipedia.org/wiki/Koloman_Moser) [sh]