From queenvictoriasfamily.tumblr.com; image enlarged.
Mary wears an 1880s dress with a cuirasse bodice over a tablier over a pleated skirt.
Keywords: Queen Mary, May of Teck, Mary of Teck, Princess, Queen, Teck family, Windsor family, British, curly coiffure, chemisette, high enclosing neckline, long under-sleeves, cuirasse bodice, buttons, long tight sleeves, tablier, close skirt, maxi-length skirt, pin