1850s evening or dinner dress in a boldly-patterned silk with copper-colored trim. Wide “pagoda” sleeves were popular throughout the 1850s and into the 1860s, but the shape changed gradually through the years. The way these are gathered at the top is more typical of the mid 1850s. The wide, shallow v-shaped waistline is also typical of the 1850s.
This is likely some kind of evening dress, for dinner or other gatherings, but not intended for formal ball wear. The wide, open neckline paired with long evening sleeves is indicative of evening wear.
(Source: Time Travelers Antiques, off ebay years ago.)