From Wikimedia; photo - Ingersoll
Countess Cosel's coiffure is short dating this to mid century; I believe the notched sleeves and neckline are hers independent of fashion.
Keywords: Ingersoll, Anna Constantia von Brockdorff, von Brockdorff family, Cosel family, Wettin family, Countess, German, mistress, Augustus the Strong of Saxony, straight coiffure, modesty piece, scoop neckline, bodice, vee neckline, notched sleeves, girdle, natural waistline, brooch, clasps, wrap, lining