From the seller:
Fancy rose pink silk ballgown dating to the late 19thc. Side closing bodice fully lined with interior stays and underarm pads, decorated with white organza, short sleeve. Skirt may have had additional underskirt, dramatic scallop hem decorated with ruffled organza and velvet ribbon. Original hardware. In overall very good antique condition the silk is strong no underam staining. Chest measures 32" waist 22" length in front 40" in back 49".
Based on the skirt shape and the sleeves, I think this is a late 1860's Fancy Dress. What we would call today costumes in the 1860's were out of this world crazy. For instance,
That is supposed to be a hand fan costume. There are tons of drawings of tea length fancy dresses, super crazy fancy dresses, regional fancy dresses - we've got nothing on what they were doing in the 1860's, really.