From www.ab-ins-gruene.de/index.php?option=com_rcevents&view=rcevents&Itemid=60&event=16.
This is a Spencer similar to the one worn by Queen Luise for her Amazon portrait.
Keywords: Queen Luise of Prussia, Königin Luise von Preussen, Luise of Mecklenburg-Strelitz, Princess, Queen, Mecklenburg-Strelitz family, Hohenzollern family, German, high enclosing neckline, neck band, tucker, Spencer, collar, frogging, buttons, long tight sleeves