Watch List notes:

Gaius, called Caligula (37-41), Aureus, Rome, AD 40; AV (g 7,63; mm 19; h 5); C CAESAR AVG PON M TR POT III COS III, laureate head r., Rv. S P Q R / P P / OB C S, in oak wreath. RIC 27; C 20; Calicò 329.
Very rare, good very fine.