I just won this one in the last CNG auction. This rarer reverse type was issued after the defeat of Maxentius. During this period, the mint of Rome struck coins for Maximinus and Licinius I also, but a few types, including this one, were struck only for Constantine I. It is also an unlisted workshop (RIC VI only lists P and Q) and is ex- Dattari.
The use of the Hercules reverse is perhaps a reference to the Tetrarchic system in which rulers belonged to either the family of Jupiter or Hercules; though there were HERCVLI VICTORI reverses issued from the East for all three rulers. On a side note-- there is also a herculean allusion from Praxagoras of Athens via the review of Photius in which Constantine was forced by Galerius to fight a lion.
http://www.constantinethegreatcoins.com/Constantine/Photius.htmlConstantine I
A.D. 312- 313
21mm 4.7g
IMP C CONSTANTINVS P F AVG; laureate and cuirassed bust right.
HERCVLI VICTORI; Hercules standing right, leaning on club and holding Victory on globe and lion’s skin.
In ex. R S
RIC VI Rome 299