Court train, First Empire
From the Chateau de Malmaison Costume Collection app:
The use of platinum metallic thread to decorate this train is an indication of its exceptional status. This embroidery includes horns of plenty and flowers in full bloom in relief, demonstrating the exceptional skill of the embroiderers who supplied the imperial court with the official costumes Napoleon demanded. The trains were attached to the dress by a system of straps concealed among the armhole pleats. At a later period, trains were simply attached by a tie below the bust. This second system of attachment was only suitable for trains made of lighter fabric, not for heavy velvet trains.”
(Source: fripperiesandfobs)