A ‘casket’ of knwoledge, the Tresor was written in France during his author’s exile years, between 1260 and 1266. Brunetto Latini (1220/30-1293), a Tuscan, chose French to draw it out, for this was the “most common and known” among vernacular idioms. The encyclopaedic work consists of three books: the first one is dedicated to theology, sacred and profane history, natural sciences with plenty of information on astronomy, geography and the animal world; the second book on ethics reports the thoughts of some moralists through the study of man’s vices and virtues; the third one deals with questions about rhetoric and politics, disciplines that are indicated as the basis for the art of government. Of the extant around 90 currently known codices of the French Tresor, among which there are complete and incomplete manuscripts or fragments, the 31 folia of the ms. U3 turn out to be ‘membra disiecta’ of a same manuscript including all the three books that were reused as cover-boards for notarial protocols between 1528 and 1535 by Nicolò Maurisio, notary in Udine, who collected therein the deeds of a judgement dealing with the Savorgnan. The manuscript belongs to the Tresor original redaction and is hence lacking of the historical supplements about the battle of Tagliacozzo (August 23rd, 1268) and the connected political events which were later added.