Olga's dress has a proto-bustle or bustle that dates this image to 1870 or, more likely, 1869. Her dress also has a forward-looking rectangular neckline while her coiffure has long sausage curls. The bodice of Maria Alexandrovna's dress is covered with a darker material (called a "stomacher" in the keywords to only mean it covers the center front of her bodice).
Keywords: 1869, Olga Nikolaevna, Tsaritsa Maria Alexandrovna, Grand Princess, Queen, Princess, Tsaritsa, Romanov family, Württemberg family, Hesse family, German, curly coiffure, long curly coiffure, high neckline, tucker, stomacher, crinoline, over-skirt, fringe, tassels