The portal was the main entrance to the so-called Banco Mediceo, the palace donated by Francesco Sforza to Cosimo de 'Medici in 1455, home to the bank branch headed by Pigello Portinari, located in via dei Bossi. Already destined to be exported to England, the monument was acquired in 1864 by the Museo Patrio Archeologico thanks to the joint financial effort of private citizens, the State and the Municipality of Milan. Although the construction events of the building are particularly rich in letters and notarial deeds, the final document that ascertains the name of the architect and explains the role played by the Lombard masters called to work on that undertaking commissioned by the Medici family is missing. Antonio Averulino, a Tuscan architect called to various construction sites promoted by Francesco Sforza, has the role of witness of the splendid factory described by 1464 in his Treaty of Architecture. An exuberant decoration covers the shoulders, the archivolt and the tympanum of the portal, filling the entire surface with natural and allegorical figures, fluted pilasters, frames, coats of arms, emblems and mottos enveloped in plant ornaments; finally, within clypei pods, the profile busts of Francesco I Sforza and his wife Bianca Maria Visconti.