Pergamum 19/18 BCE         Obverse type (not shown): bust of Augustus Reverse TYPE: temple of Mars Ultor (Mars the Avenger) housing standards LEGEND: MART(is) ULTO(ris)

In 42 BCE, at the battle of Philippi (where he defeated Caesar's assassins), Octavian had vowed a temple to Mars Ultor (Mars the Avenger). The permanent temple was not built until 2 BCE, but a temporary circular temple, shown in this type, was built and the recovered standards housed there in 20 BCE.

"of Mars the Avenger"