66 Via Trento

66 Via Trento was a house in Florence that was owned by Piero de' Medici. He instructed Greco to kidnap his own son, Lorenzo and his fiance, Angelica Visconti, and leave them there so that they could blame Milan. with two keys for the property, he gave one key to Greco, and the other to Placidi.

History
A badly injured Placidi, betrayed by his master, revealed the truth to Lorenzo by giving him the key. Although in denial, when the key fit the door, Lorenzo realised the person his father truly was. (The Dogs of War)