Ferdinand III died on April 2, 1657, making any ducat struck that year potentially a posthumous issue depending on mint production timing — Vienna continued striking coins in a deceased emperor's name until the new reign was formally proclaimed. Her#210 identifies this as a Vienna product, distinguishable from the Graz and Prague issues of the same reign by die characteristics catalogued by Herinek.
Ferdinand III died on April 2, 1657, making any ducat struck that year potentially a posthumous issue depending on mint production timing — Vienna continued striking coins in a deceased emperor's name until the new reign was formally proclaimed. Her#210 identifies this as a Vienna product, distinguishable from the Graz and Prague issues of the same reign by die characteristics catalogued by Herinek.