From ARTExplorer's photostream on flickr.
Lady de la Pole's dress has what appears to be a buttoned vest bodice with sawtooth-edged straps over her chemise that provides the sleeves of her dress in this 1786 Romney portrait.
Keywords: 1786, Romney, British, bouffant coiffure, hat, ribbon headdress, chemise, scoop neckline, elbow length balloon sleeves, engageantes, vest bodice, buttons, vee waistline, full skirt, shoes