Obverse: Bare head of Caligula (Gaius) right. Text around C CAESAR AVG GERM P M TR POT COS .
Reverse: Radiate head of Divus Augustus right, flanked by two six-rayed stars.
History: Upon the death of Tiberius on the 16th of March, 37 AD, the commander of the praetorian guard, a man named Macro, insured the smooth succession of Caligula to the imperial throne.
The first coinage of Caligula (Gaius) usually portrayed his own portrait along with that of his grandfather Augustus, his father Germanicus or his mother Agrippina. Augustus had been Emperor and Germanicus, well loved by the people of Rome, was the nephew of Tiberius. These coins therefore made a strong political statement that showed that Caligula had the legal right to the throne.
Date: Lugdunum mint, 37-38 AD
My thanks, as always, to http://www.dorchesters.com for their excellent information.