Fernando VII was King and he was married to Maria Josepha Amalia of Saxony when this dress was worn.
From fripperiesandfobs.tumblr.com.
The triangular panel in back was a feature of early post-Napoléonic dress. The cherusque or ruff is a Napoléonic era holdover.
Keywords: 1820, Spanish, neckline ruff, quarter length puffed sleeves, cuffs, waist band, bows, natural high waistline, train, close skirt, court dress