A large Art Deco rectangular diamond brooch, 1920s

gold, platinum (unmarked), 1 central round brilliant cut diamond weighing approx. 1,29 ct J/VS1, 2 diamonds weighing in total approx 0,06 ct H-I/VS-SI, 76 rose-cut diamonds weighing in total approx. 0,20 ct, 34 8/8 cut rock crystals weighing in total approx. 0,60 ct, synthetic sapphires, weight: 21,15 g