There's an auction at Christie's of items that had belonged to Angela Lascelles (Princess Mary's daughter-in-law) that include many items that once belonged to Queen Mary:

QUEEN MARY'S CHINESE STYLE COAT AND SKIRT A TURQUOISE SILK COAT IN THE CHINESE STYLE
A lady's silk overcoat, remade from a Chinese Imperial-style robe, incorporating eight roundels embroidered with five-toed dragons, labelled Reville, Paris, London to the interior pocket and 'H.M. The Queen'; and an associated pale lemon apron skirt, altered with wadding, appliqued embroidery, and the remains of fur trim
Reville, the London couture house was founded in 1906 by William Reville. In 1910, it was appointed Court Dressmaker for the Queen's Coronation robes. In 1936, Reville merged with the House of Worth. The 1920s saw a revival in exotic influences from Japan and China amongst women of style; Queen Mary wore a very similar overcoat on the occassion of her first visit to a cinema with H.M. King George V in 1924.