I won this one at auction a while ago; didn't realize my photos were out of focus until it was already up in its album! Anyway, this is probably my favorite reverse of any Roman coin.
Faustina II, Wife of Marcus Aurelius
AR Denarius
FAVSTINA AVGVSTA, draped bust right, wearing stephane (tiara)
SAECVLI FELICIT (The Joy of the Age), Twin toddlers Commodus and Antoninus playing on throne
Minted ca. 161-165
RIC 712

The marriage of Faustina Minor and Marcus Aurelius was initially a political arrangement to solidify acceptance of Antoninus Pius' adoptive son as his rightful successor. Regardless, they grew affectionate of one another and enjoyed a happy and fertile marriage. They had 13 children together, of whom only five survived to adulthood. This coin in particular commemorates the birth of Commodus and Antoninus, both born in 161, just a few months after the death of their grandfather Antoninus Pius, the first biological heirs apparent in nearly a century. Antoninus died around age 4, in 165.
Commodus of course went on to become a decadent, bloodthirsty, insane tyrant, but for the moment crystallized on this coin, he was just an innocent child who spit out his peas and threw tantrums at nap time. Rome felt secure in her future, with no end to her glory in sight.