Some things are meant to happen. I had been watching this one on Vcoins since January or December, and came close to pulling the trigger a few times. I had also been watching a coin on Agora, but bidding went over where I could justify the cost. Not five minutes later I get the email that this coin has been discounted!

(Seller's photos)
Aemilian BI Antoninianus
c. July-October 253
IMP AEMILIANVS PIVS FEL AVG, radiate, draped and cuirassed bust right.
IOVI CONSERVAT Jupiter standing, head left, holding thunderbolt & spear, protecting a small figure of the emperor.
RIC 4
Marcus Aemilius Aemilianus was born in Roman Africa during the early Severan period. His early life was either undocumented or purged from records, and he enters history in 251 upon being sent by Trebonianus Gallus to maintain Roman army presence in Moesia along the Danbue, taking the new emperor's place as governor of the province.
Gallus was only able to leave his post by buying peace with the Goths at a humiliating price, to be paid as an annual tribute. Whether by character or through circumstance, Gallus could not maintain the empire, and it began to crumble. Morale was dangerously low within the army. Claiming they had not received their tribute, and in the summer of 253 the Goths crossed into Roman territory and began raiding and pillaging. Aemilian acted decisively, and crushed the invaders and then crossed the Danbue to hit them at their heartland. Revitalized, the troops proclaimed the victorious general-governor as Emperor in July or August 253. He set out for once for Rome.
Gallus and his son Volusian gave battle, but after several defeats, the troops defected and the emperors were murdered. Shortly before their final defeat, they sent for their ally Valerian, who was in control of a large force. The Senate opposed yet another "low" emperor (they were similarly unhappy with Maximinus Thrax and Philip) but eventually ceded the titles to this new claimant. Apparently the office of the consulship was withheld, due to Aemilian's non-Senatorial background.
--Side note: In particular, I was fascinated with the usual inclusion of "Pius" in Aemilian's titles. What had he done to deserve it? After doing a little digging, it appears that in his negotiations with the Senate, Aemilian vowed to use his position as emperor to neutralize the threat of the Goths and the Persians, and then
dissolve the position of the Emperor, returning actual control back to the Senate . Whether this was just hot air is impossible to determine, but it's an interesting tidbit.--
Anyway, no sooner had Aemilian consolidated his position than word of Gallus and Volusian's death reached Valerian, still en route with reinforcements. Valerian was proclaimed emperor, and Aemilian was murdered by his own fearful troops. The Senate enacted a darn atio against Aemilian, and it is probably only thanks to the rampant inflation of the time that his coins are even attainable to a collector of modest means.
Aemilian was my last gap in the legitimate emperors of the Crisis, which I define as the stretch from Gordian III (after the 238 civil war) until the establishment of the Tetrarchy. I am still missing most of the unsuccessful usurpers, in addition to Marius from the Gallic empire. Missing several wives as well. But, it feels good to finally fill that hole!