The Codex was manufactured for Antonio Pancera, patriarch of Aquileia and cardinal of St. Susanna († 1431): his coat of arms, very similar to the family Tomacelli’s one, is twice drawn on the lower border of f. 1r, on the right and left sides of Pietro Tomacelli’s coat of arms, pope with the name of Boniface IX. The codex was full-page written by one only copyist. The first and most important section of the ms., on ff. 1r-19r, consists of Notabilia drawn from the twenty-four books of Francesco Petrarca’s Familiares; it is here dealt with a systematic collection of moral sayings: each single epistle had been screened, and from each of them either ‘sententiae’ were drawn for their assessed exemplarity or a brief summary. On ff. 20v-21v, there is a poem by Friar Giovanni d’Adria, bishop of Ostuni, in praise of Pancera, rich in information about the cardinal’s biography. The collected texts in the Guarnerianus ms. 138 evidences peculiar coincidences with the collection contained in the Guarnerianus ms. 220, which was also written for cardinal Pancera. Even more than the Guarn. ms. 138, the Guarn. ms 220, with the collected epistles in the opening and the following celebrative poem, makes out an apology of the cardinal, functional to document his good faith and rectitude in the patriarchal governance.