1. The old term was still retained, as in the Council of Chalcedon, where the prominent purpose was to commend the bearer of the letter, whether cleric or layman, to the favor and good offices of another bishop.
2. The same letters were also known as "canonical" in accordance with the rule of the Church." This is the word used in the letter from the synod of Antioch, by the councils of Antioch and Laodicea. The Latin equivalent seems to have been the literae formatae, i.e., drawn up after a known and- prescribed form, so as to be a safeguard against imposture. It was stated at the Council of Chalcedon by Atticus, bishop of Constantinople, that it was agreed by the bishops at the councils of Nicaea that every such letter should be marked with certain letters, in honor of the three Persons of the Trinity. In the West the signature or seal of the bishop was probably the guarantee of genuineness. The first mention of the use of a seal-ring occurs, it is believed, in Augustine.
3. From the use of the letters as admitting clergy or laymen to communion they were known as comnunicatoriae in Latin, and by a Greek equivalent.
4. The literae pacificae appear to commend the bearer for; eleemosynary aid. They are to be given to the poor and those who need help, clerics or laymen; especially, according; to the Greek canonists, to those who had suffered: oppression at the hands of civil magistrates. Thel word is used also by the Council of Antioch, as applied to letters which might be given by presbyters as well as bishops,
5. There were “letters dimissory,” like those of modern times. The word is of later use than the others, and occurs first in the council in Trullo, in a context which justifies the distinction drawn, that it was used in. reference to a permanent settlement of the bearer, "commendatory," when the sojourn in another diocese was only temporary.