I believe on the OP coin the head is that of Sol, while on my coin posted above the head is that of Serapis.
Here's two of mine.. Maximinus ll 309-313 AD. Alexandria mint.. AE Follis 5.01g. Head of Serapis Maximinus ll 309-313 AD. Antioch Mint AE Follis 4.88g. Head of Sol
I don't know why but I am always really drawn to the folles from this period. They keep catching my eye whenever I see them. Excellent coin JA
I'm momentarily reviving this thread because the coin in the OP arrived today and it turns out to be a very pleasing brown/rust color. I lighted the reverse in such a way to accent the fruit in the cornucopia. Also, to acknowledge Bing's correction: yes, Genius is holding the head of Sol, not Serapis. My mistake. Here is the complete attribution and true-color pic. Maximinus II as Augustus, AD 308-313 AE Follis, 21mm, 5.12g, 12h; Antioch mint: 312. Obv. IMP C GAL VAL MAXIMINVS P F AVG; Laureate head right, parallel laurel ties. Rev.: GENIO-AVGVSTI; Genius standing facing, modius on head left, naked but for chlamys over left shoulder, head of Sol in r. hand, cornucopiae in l.; star / A // ANT. Reference: RIC VI, Antioch 164b (p. 643).