MEXICO. Cob 4 Reales, ND (1554-56)-Mo O. Mexico City Mint. Carlos & Johanna. PCGS AU-58. KM-18; Cal-138. Weight: 13.60 gms. Late Series. Fairly well struck for this oft crudely produced issue, presenting some charming toning to the surfaces and even some glints of brilliance remaining in the protected areas.