The Court dress of old was really two similar, but different costumes. The first variety which I've called the State robes were worn by the royal ladies to the Ceremonial Opening of Parliament in January each year and apparently at the Court cour until 1952 (I think so, but haven't been able to find much information on the subject of the cour). While the cut of the dress itself varied during the 19th century to adapt to different fashions the look became set by the later decades of the century and remained largely unchanged until 1974. It was for instance Queen Fredrika who added the arms and long train modelled on the court dress of St Petersburg after spending time there with her sister Empress Louise. The black and white sleeves have managed to survive for almost 230 years and I'm certain that they'll be there for as long we have a court. That the dress stopped being subjected to the whims of fashion was mostly because of an eventual sense of tradition, but also because of economics. They weren't worn frequently and were very expensive to make. The Haga princesses inherited theirs from older relatives. Princess Christina for instance inherited her dress from Princess Ingeborg.
The dress worn by the ladies of the court and the wives of the members of government was the blue print for today's court dress. Much simpler than the state robes it's style was changed with the fashions, but were always black, had the characteristic arms and a train. The ladies of the court lined the decolletage with lace, but as can be seen during at least the 60s and 70s many wives of the members of government and others chose not to. It was quite common for ladies to borrow dresses from each other, rent a whole dress or even just rent the sleeves and a train and have them attached for the day to a black gown they owned.
This variety was also worn by the wives of foreign diplomats introduced at the court during the cour until the 1920s and by young ladies introduced at the court during the cour up until 1952. After that the requirement to wear a special dress was abolished. The cour itself was abolished by Queen Louise in 1962 and replaced with "democratic lunches for professional women".
The court dress worn by the ladies of the court today is both modelled on the simpler varieties worn during the 60s and 70s, but also on the empire style worn during the early 19th century and yes, it does have a bit of an 80s air too, doesn't it.
