Severina, wife of Aurelian. Augusta 274-275 A.D. -  AE Antoninianus - 23.46mm, 3.53g
Obverse - SEVERINAE AVG
Severina, her diademed and draped bust right, resting on a crescent.
Reverse - CONCOR-DIAE MILITVM
VIXXI in Exergue
Concordia standing left, holding standard in each hand.

The image below was photographed by Jeroen van der Meulen from RomanCoinShop. The image above is my own scan.
Severina
Minted at the 6th officina (VI) in Siscia (Sisak, Croatia) in 275 A.D.

Reference: 
Webb, P.H., "Roman Imperial Coinage", Volume 5, Part 1 (RIC), p317, nr. 13.
Sear, D.R., "Roman Coins and their Values" (RCV Millennium Edition), Vol. 3, p439, nr. 11706.
Cohen, H, "Descriptions Historique des Monnaies frappees sous l'Empire Romain" (C), Vol 6, p210, nr. 8.
Van Meter, D., "Handbook of Roman Imperial Coins" (VM), p258, nr. 4.
Suarez, R., "Encyclopedia of Roman Imperial Coins II" (ERIC II),  p642, nr. 64 (B2, O4, R04, T2, M6, Exe: VIXXI)
Kampmann, U., "Die Münzen der Römischen Kaiserzeit", 2. Auflage (KM2), p352, nr.107.3

Quality: Very Fine