Is "Ducat of Charles VI, Holy Roman Emperor, King of Hungary (r. 1711–40)" in the public domain?

Yes, Ducat of Charles VI, Holy Roman Emperor, King of Hungary (r. 1711–40) is in the public domain and available for free download under CC0 license.

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Ducat of Charles VI, Holy Roman Emperor, King of Hungary (r. 1711–40)

Unknown Artist, 1730