A collection of sixty-nine business letters, dated between 1616 and 1625, of which twenty-two are addressed to Nicolò Gianni (also spelled "Niccolò Giani") and Lorenzo Segni; three to Lorenzo Segni alone (1624–1625); and twenty-six to Lorenzo Segni and Francesco Medici (1625-1634). The correspondence originates from agents based in various Italian cities as well as Spain (specifically Madrid, one letter, Burgos, two letters, and Cuenca, three letters) and relates commercial and financial matters, including business transactions, expense accounts, and price comparisons.

Some letters refer to the wool trade, while others mention the cochineal dye trade (a brilliant red dye derived from insects native to South America, which was flourishing in Spain and Genoa at the time). Among the correspondents, the names of the Pallavicino and Donghi families stand out—two of the most influential families in late-Renaissance Genoa.