Costanzo was both a painter and a medalist who worked chiefly in Naples, his family remaining in Ferrara. His date of birth is uncertain, and he died after 1524.
Costanzo was called to Istanbul, at an uncertain date, with a commission to paint a portrait of the sultan. This probably occurred during the period 1475-1478 when diplomatic relations were restored following the Turkish attack on Negroponte of 1470. The sultan had requested "uno pittore de quelli dal canto di qua" (a painter from over here). It is likely that Costanzo remained in Constantinople until the death of the sultan in 1481. The only document for the visit is a letter from the Ferrarese envoy to Naples, Battista Bendidio, to Ercole d'Este that reports that Costanzo was being well treated and had been made a cavaliero (knight) at the court.
The artist is again recorded in Naples in 1485, when he painted a portrait of Ferdinando d'Este. In August of that year he was in Ferrara.
No documented painting by Costanzo is known, but he is possibly a more important artist than has been allowed. Three famous drawings made in Constantinople, traditionally ascribed to Gentile Bellini, may be by Costanzo.[1]
[1] Julian Raby, "Pride and Prejudice: Mehmed the Conqueror and the Italian Portrait Medal," Studies in the History of Art 21 (Italian Medals, ed. J. Graham Pollard) (1987): 176.
[Published in: John Graham Pollard. Renaissance Medals. The Collections of the National Gallery of Art Systematic Catalogue. 2 vols. Washington, 2007]