Grading: Its isnad is da'if (weak).
Technical note / Defect ('illah): The reason for this is the "idtirab" (inconsistency) of Muhammad bin Ishaq in the isnad, as al-Hafiz Ibn Hajar explained in "Fath al-Bari" 21/ 497 - 499. Al-Bukhari, in "al-Tarikh al-Kabir" 2/ 25, pointed to the different versions of its isnad from Ata', and then to the disagreement over it from Muhammad bin Ishaq; then he cited the hadith of Ibn Umar in which the price of the shield is estimated at three dirhams — and it is in his "Sahih" (6795) and in "Sahih Muslim" (1686) — and said: This is more authentic. Likewise al-Nasa'i clarified the disagreement in its isnad in "al-Sunan al-Kubra" 7/ 29 - 32, and al-Bayhaqi also set out the disagreement in "al-Sunan al-Kubra" 8/ 256 - 257 and in "Ma'rifat al-Sunan wa al-Athar" (17089 - 17092), and he also declared it "ma'lul" (defective) because of Muhammad bin Ishaq's contradiction (of others).

Important point: Ibn Abd al-Barr said in "al-Tamhid" 14/ 381: Of all the isnads that have come mentioning the shield (mijann), none is more authentic, in the view of the scholars of transmission, than the isnad of the hadith of Ibn Umar.

Corroborating chains and supporting reports: It was narrated by Abu Dawud (4387) and al-Nasa'i (7397) via Ibn Numayr, from Ibn Ishaq, with this same isnad, as the statement of Ibn Abbas (mawquf).

Note / Clarification: See the rest of its takhrij and the discussion of it in "Sunan Abi Dawud" (1387), al-Risalah al-Alamiyyah edition.