When it was discovered in late 1553 near Arezzo, southeast of Florence, along with some smaller bronzes, it was quickly claimed by Cosimo I de' Medici, then the Duke of Florence, later the first Grand Duke of Tuscany, and the founder of the Uffizi.
WSJ: The Imaginary Made Nearly Read | The Chimera of Arezzo | Masterpiece by Judith H. Dobrzynski