328-329 AD., Helena, Siscia mint, Æ3 / Follis?, RIC 218.

Helena, Siscia mint, officina 5, 328-329 AD.,
Æ3 / Follis? (18-19 mm / 2,76 g), bronze, axis about medal alignment ↑↑ (ca. 20°),
Obv.: FL HELENA - AVGVSTA , bust of Helena right wearing ornamental mantle and necklace, hair on the neck tied up in a jeweled diadem - buste diadémé et drapé à droite.
Rev.: SECVRI TAS - REI PVBLICE / Є SIS (crescent in crescent) , Securitas, draped and veiled standing facing, head turned l., holding drapery with her l. hand, laurel-branch in her lowered r. Hand - la Sécurité debout à gauche tenant une branche dans sa main droite, ESIS croissant surmonté d’un autre croissant à l'exergue.
RIC VII, p. 453, no. 218 (C2) ; 60 pieces of RIC 218 on www.nummus-bible-database.com , 37 from officina 5 .

Helena, mother of Constantine I, had died in 328 or 329 AD. Her reappearance on the coinage with reverse Public Peace in 337-340 should be connected to the succession of her three grandchildren Constantine II, Constantius II, and Constans in 337, after the assassination of Dalmatius, Hannibalianus, and other descendants of Constantine I's stepmother Theodora who were regarded as their potential rivals.
See J. P. C. Kent, RIC VIII, pp. 7 and 33.