He died in 1928; she in 1952.
From Miss Mertens' photostream on flickr.
The caption about wartime memories suggests this portrait of Hilda and Ferdinand II of Baden was issued well after the photo was taken.
Keywords: Hirsch, Grand Duchess Hilda of Baden, Nassau family, Baden family, Grand Duchess, German, straight coiffure, blouse, high enclosing neckline, vest over-bodice, long close sleeves, cuffs, blouson bodice, close skirt, necklace