A few spots in the background removed with Photoshop and sepia tone removed by gogm.
There are many portraits of her wearing gorgeous dresses and jewels. This one shows an open side of her sleeves fastened with cloth ropes.
Keywords: W. & D. Downey, Queen Mary, Princess, Queen, Teck family, Windsor family, British, curly coiffure, tiara, quarter length tight sleeves, tassels, bateau neckline, modesty piece, stomacher, waist band, shallow vee waistline, close skirt, order bows, choker necklace, necklace, draped necklace, earrings, bracelets