Constantine I (307-337 A.D.) -  AE Follis - 19.34 x 19.62mm, 5.64gr
Obverse - IMP C FL VAL CONSTANTINVS P F AVG
Constantine I, his laureate head right, with parallel laurel ties.
Reverse - GENIO-AVGVSTI                              
Genius standing left, modius on head, naked but for
chlamys over left shoulder (the chlamys falls low), head of
Sol in right hand and cornucopiae in left.
Star in left field ΓI in right field, ANT in Exergue.

The image below was photographed by Beast Coins. The image above is my own scan.
Minted at the 13th officina (ΓI) in Antioch (Antakya, Turkey) 312 A.D.

Reference:
Sutherland, C.H.V., "Roman Imperial Coinage", Vol. 6 (RIC), Antioch, p643, nr 164c (Unattested officina ΓI).
Voetter, Otto, "Die Münzen der römischen Kaiser, Kaiserinnen und Caesaren von Diocletianus bis Romulus, Katalog der
hinterlassenen Sammlung und Aufzeichnung des Herrn Paul Gerin" (Voetter-Gerin), Antiochia, Constantine Magnus, p47, #15.
Sear, D.R., "Roman Coins and their Values" (RCV Millennium Edition), Vol. 4, p449, nr. 15903.
Suarez, R., "Encyclopedia of Roman Imperial Coins II" (ERIC II),  p851, nr. 784-792 var officina ΓI 
                                                                                           (B59, O49, R74, T137, M2, EXE: star/ΓI/ANT)
Failmezger, V., "Roman Bronze Coins From Paganism To Christianity 294-364 A.D." (Failmezger), nr 190pCI.


Quality: Very Fine+
Rarity: Scarce
Ex Voz Collection of Roman Imperial Tetrarchy.
Vozmozhno's site www.tetrachy.com is no longer online but Beast Coins still has some of his coins (including this one) listed here.
This coin is also featured on Not in RIC.