Trebonianus Gallus, Antioch mint, 252-253 AD.,
Antoninianus (20-21 mm / 4.01 g),
Obv.: IMP CC VIB TREB GALLVS PF AVG , radiate, draped, cuirassed bust of Trebonianus Gallus right, seen from behind.
Rev.: [IV]NO MAR-TIALIS , Juno, draped and diademed, seated l., holding transverse scepter in her l. hand, grain-ears in her r. hand resting on her r. knee.
RIC 168, 83 ; C 47 .
This type is found only in the second (coarse portrait) issue (the later Antioch issue). Its engraving is of inferior quality - both signs of an emergency requiring rapid army mobilization against Antioch's foes to the east.
In 1975, a hoard of coins minted under Gallus at the Antioch mint in Syria was analyzed by William Metcalf.
Metcalf found that the Antioch mint had produced nearly ten times as many coins during the second half of Gallus' reign as it had during the earlier years. In addition, the later coins were of a crude style and frequently had spelling and mint mark errors. This massive and apparently hasty increase in production indicates a pressing military need in the eastern provinces, as does one of the main coin types of Antioch: MARTEM PROPVGNATOREM; ""...the type appears only in the last issue of Antioch; what is more, Mars is invoked not in his usual aggressive aspect ... but instead as propugnator: literally a protector or defender of a place"" (Metcalf).
What emergency would require the mint to strike so many coins in such a rush, and what was Mars being called on to protect against? Almost certainly the Sassanid Persians. Historians had long known that Shapur the Great, the Sassanid king, had invaded the eastern Roman provinces at some time during the decade of 250 A.D., but these coins provide strong specific evidence that the invasion took place in the spring of 253 A.D. before Gallus was deposed by Aemilian but after Gallus had conducted a massive minting operation for that year.
(from R. Beale´s site: http://sonic.net/~rbeale/mysite/... )