"a design style of late 19th century origin characterized especially by sinuous lines and foliate forms". It was preceded by the Victorian style and followed by Art Déco. Some the pioneers of Art Nouveau include Alphonse Mucha, Hector Guimard, Charles Rennie Mackintosh, Gustav Klimt, Antoni Gaudí i Cornet, and Louis Comfort Tiffany.
The movement encompassed architecture, painting, sculpture, jewelry, and household items, such as this vase. I have hunted and can find no marks on it to indicate who made it, where it was made, or exactly when it was made.
I am risking a guess that it was made in Britain or France because the feet are dolphins, which appear in symbolism in those two countries. At the top of the brass handles there are stylized creatures, either lions or green men. At about midway down the handles are what appear to be cockatrices with open beaks. Leaves and flowers adorn the four panels encircling the base. The ceramic portion of the vase is in good condition, with no cracks, chips, or repairs. It will be packaged with bubble wrap to ensure a safe journey to begin its next phase with you. Please see the photos as they are a part of the description. The vase measures 16 inches tall, 10 inches at the widest point including handles, and 6 inches at the side without handles. It weighs just over 5.5 pounds.