Constructive research: In SOTN, we're kinda on the cusp of the Regency. Rococo starts it's fall out of favor in the fashion in both France and England, and those who wore it were considered 'behind' in the times. (This is why Alucard wakes from his slumber, still wearing it. :3) This image is between 1795 & 1797. Maria's outfit is a combo of a Regency sleeve & neckline, with the silhouette of a curaco/juste-au-corps from the late 1780's.