As will be seen among the Canons of Chalcedon, the old name, Letters Commendatory, is continued, but in this canon and in the 41st of Laodicea the expression “Canonical Letters” is used. In the West, at least, these letters received the episcopal seal of the diocese to avoid all possibility of imposture. Dean Plumptre (whom I am following very closely in this note) believes the earliest evidence of this use of the diocesan seal is in Augustine (Epist. lix. al. ccxvij.) He also refers to Ducange, s.v. Formatæ.