Claudius. AD 41-54. Æ Sestertius (36mm, 24.84 g, 6h). Rome mint. Struck AD 42-43. Laureate head right / Spes advancing left, holding flower and raising hem of skirt; c/m: NCAPR (Nummus Caesare Augusto PRobatus?) within rectangular incuse. RIC I 115; von Kaenel Type 70; c/m: Pangerl 60. Brown patina. Coin: Good Fine; c/m: Near VF.
This countermark, one of the most common imperial countermarks, is likely a validating countermark used during the reign of Nero. For further discussion, see Kraay, "The Behavior of Early Imperial Countermarks" in Essays Mattingly, pp. 132ff.