Maximianus. 286-305 AD. AV Aureus, 5.54 g. AD 293-294. 
Rome mint. 

MAXIMIA-NVS PF AVG, laureate head right.
HERCVLI DEBELLAT, Hercules standing right, grasping one of
the heads of the Lernean hydra and wielding club, whilst the 
hydra wraps its tail around Hercules' left leg.
Mintmark PROM. 

Calicó 4662; Cohen 255 var (Hercules left). 
Apparently only the second recorded specimen with Hercules 
standing right on this reverse image.

With permission Gemini, LLC - Auction 12, Lot 427, Jan 2015