This antoninianus was struck under Philip I Arabs in Rome in 248 AD, and is part of a series of coins celebrating the 1000th anniversary of Rome.
A saeculum was typically 100 years, and was regarded as the longest possible lifespan for a human. So every 100 years they would have games called the Ludi Saeculares, and in AD 248 they coincided with the millennial celebration.
The coins struck to celebrate this occasion have a wide variety of cool reverses; wolves, stags, goats, hippos, lions, etc. They are cool and common.
A very small subset of them have the animals going in the opposite direction to the norm. Maybe they were test issues, maybe it's just a coincidense. This coin has the stag going left instead of right and is, imho, really really pretty.
Obverse: IMP PHILIPPVS AVG, radiate, draped & cuirassed bust right Reverse: SAECVLARES AVGG, stag walking left
RIC 20, 3.88g, struck in Officina V(5)
Thank you :) Yes, the scale of things when you collect ancient coins is sometimes staggering. Like, this coin is 500 years removed from the 1st Punic war, Philip I was as close to Scipio Africanus as we are to Elizabeth I or Christian IV of Denmark.