The Book of Occultation — al-Ṭūsī · Hadith 553 (#Ḥadīth #1)

فأولهم: من نصبه أبوالحسن علي بن محمد العسكري وأبومحمد الحسن بن علي بن محمد إبنه عليهم السلام، وهو الشيخ الموثوق به أبوعمرو عثمان بن سعيد العمري رحمه الله وكان أسديا وإنما سمي العمري:

Abu Amr Uthman bin Saeed Amari, He was the first emissary during the period of occultation, who was appointed to this position by Imam Hadi and Imam Hasan Askari . He was a trusted elder of the society. His name was Abu Amr Uthman bin Saeed Amari, may Allah have mercy on him. He belonged to the Asadi tribe, but was named as Amari.

Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).