Filarete completed his substantial book on architecture sometime around 1464, which he referred to as his "Libro architettonico" ("Architectonic book"). Neither he nor his immediate contemporaries ever referred to it as a "Trattato" ("Treatise"), though it is usually now called such. The "Libro", which comprises twenty-five volumes, enjoyed a fairly wide circulation in manuscript form during the Renaissance. The most well known and best preserved copy of the "Libro" is a profusely illustrated manuscript known as the "Codex Magliabechiano" (probably drafted 1465; now held in the archives of the ). The fact that the "Codex Magliabechiano" is dedicated to Piero de' Medici and was conserved in Florence suggests that Filarete was well regarded in his native Florence despite his loyalty to Milan.