From the museum's Web site.
The caption says 1860s, but the early 1870s is a more likely date given Wilhelmina's elaborate coiffure and elaborate bustle dress.
Keywords: Gosta Florman, Wilhelmina Kempe, Wilhelmina von Hallwyl, Anna Fridrica Wilhelmina von Hallwyl, Countess, Swedish, high straight coiffure, ribbon headdress, neck band, high neckline, neckline ruff, long close sleeves, cuffs, frills, bustle, over-skirt, necklace, pin