Watch List notes:

Gaius, called Caligula (37-41), Denarius, Rome, AD 40; AR (g 3,83; mm 19; h 7); C CAESAR A[VG PON M] TR POT III COS III, laureate head r., Rv. S P Q R / P P / OB C S, in oak wreath. RIC 28; C 21.
Very rare, lustrous, about extremely fine.