Court train, First Empire
From the Chateau de Malmaison Costume Collection app:
“The exquisite embroidery on this train is a clear indication of its imperial ownership; it would certainly have been worn to an important event such as a wedding, an official ceremony or a commemorative event. However, we cannot be more precise as the full-length portraits of Empress Josephine rarely show her in court outfits that match those now held in the current collections.”