The duke is wearing a French-style costume and a doublet - a typical men's garment, lightly padded, generally used by people of an average social status - with open sleeves from which the many folds of the shirt stick out. Instead of trousers, he's wearing the "rhingrave", a kind of pleated skirt that was very popular in the second half of the 17th century. He also has a large organza collar, with embroidered edges and tassels.
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