Fausta, daughter of Maximian,
2nd wife of Constantine I,
mother of Constamtine II, Constans and Constantius I
 (born ca. 289 A.D. - died 326 A.D.)
-  AE3 Billon Centenionalis - 20.68mm, 3.04g
Obverse - FLAV MAX-FAVSTA  AVG
Fausta, her bare-headed draped bust right.
Reverse - SPES REIP-VBLICAE
SMKB dot  in Exergue
Fausta standing facing, head left, holding two children
(Constantius II and Constans) in her arms. 
The image below was photographed by Caribou Coins. The image above is my own scan.
Minted at the 2nd officina (B) in Cyzicus (Balkiz, Turkey) in 325-326 A.D.

Reference:
Bruun, P.M., "Roman Imperial Coinage", Volume 7 (RIC), Cyzicus, p649, nr 40.
Failmezger, V., "Roman Bronze Coins From Paganism To Christianity 294-364 A.D." (Fm), nr 357H
Carson, R.A.G., Hill, P.V., & Kent, J.P.C., "Late Roman Bronze Coinage" (LRBC), Part I, p28?, nr 1178.
Sear, D.R., "Roman Coins and their Values" (Sear RCV 4th Revised Ed.), p329, nr. 3908, var with SMKA dot mint mark.
Sear, D.R., "Roman Coins and their Values" (Sear RCV Millennium Ed.), Volume 4, p511, nr 16578
Suarez, R., "Encyclopedia of Roman Imperial Coins II" (ERIC2),  p887, nr.47 (B1, O1, R3, T3, M5, SMKAdot)
Suarez, R., "Encyclopedia of Roman Imperial Coins II" (ERIC II-digital), p??, nr.47 (B1, O1, R3, T3, M5, SMKAdot)
Cohen 17
Van Meter, D., "Handbook of Roman Imperial Coins" (VM), p293, nr 3, reverse legend variety
Kampmann, U., "Die Münzen der römischen Kaiserzeit" (K, 2e Auflage), p426, nr. 139.4.

Quality: Very Fine
Rarity:  R2 (Rare)