"Italian nobleman" is French Duke

Nye, American auction house, sell on 2 June 2015 a "portrait of an Italian nobleman", estimated at $300 to $500.

As the inscription makes clear, it is a portrait of the French duke Charles de Chaulnes. He was an ambassador of the French King in Rome, which explains the Italian inscription on his portrait: "Carlo Ducha di Chaulnes Amb(re) della corona di Francia. 1669" basically means "Charles, Duke of Chaulnes, Ambassador of the French Crown. 1669".

No idea how much interest such a painting generates in France (do they have a National Portrait Gallery?), and what it should be worth. It is a competent but far from brilliant portrait, and the sitter is not that important in the grand scheme of things, so the estimate may be not too far off. UPDATE: sold for $1,900, so quite a way above the estimate in the end!