Amadio was a Milanese who worked as a medalist, goldsmith, seal engraver, and enameler. He was the son of Antonio Amadei di Castronago, and his will was dated in Ferrara, 6 August 1483. He had worked as a goldsmith for the court of Ferrara between 1437 and 1482 and is known to have produced ornaments for a book for Cecilia Gonzaga of Mantua in 1469. It has recently been discovered that Amadio also made the binding for the famous Bible of Borso d'Este. There are two signed medals by him of Leonello and Borso d'Este, of before 1441, and two medals of Niccolò III d'Este attributed to him. Incorrectly dating one of these attributed pieces with a reverse of the arms of Este (Hill, Corpus, 1930, no. 73, 74), Patrignani claimed in error that the medals by Amadei preceded those of Pisanello. Roovers refuted the case.
The signatures of Amadio describe him as aurifex (goldsmith). His technique of medal making was unusual and reflects his experience as a metal worker. Contrary to the usual practice of preparing the models of the effigy and inscription together on the same base, he prepared them separately, cutting the inscription into a moveable ring that would be positioned around the model of the type. The combined elements were then pressed into a mold for casting. This technique is revealed by the existence of examples of his medals in which the relative location of portrait type and inscription differ. The method was also used by Gianfrancesco Enzola of Parma (active 1455-1478) and by some medalists employed at the court of Pope Paul II.
 Giordana Mariani Canova, in La Bibbia di Borso d'Este. Commentario al codice, Modena, 1997: 252; Elena Corradini, "Medallic Portraits of the Este," in The Image of the Individual, ed. Nicholas Mann and Luke Syson, London, 1998: 194 n. 26.
[This is the artist's biography published in the NGA systematic catalogue of Renaissance medals.]