From Christie's Web site; filled in shadows to bring out the details of the dress. Also posted towards the end of the Middle 1500s - 1550 to 1590 Album.
Ruffs often hide their origins, but this ruff can be seen sprouting from a white under-garment. This is presumably mourning dress.
Keywords: 1600, Rubens, Margherita Gonzaga, duchessa di Ferrara Modena e Reggio, Gonzaga family, Este family, Duchess, Italian, wavy coiffure, headdress, earrings, lace wide ruff, vee neckline, fitted under-bodice, jacket over-bodice, vee nckline, lapels, tabbed hanging sleeves, bows