Divus Romulus. 309-312 AD. AE Follis. 

IMP MAXENTIVS DIVO ROMVLO NV FILIO, bare head right / 
AETERNAE-MEMORIAE, Domed shrine, no columns, with arched or 
flat-topped doors, surmounted by eagle, wings spread, 
standing right.

Mintmark MOSTT.

RIC VI 34.