I recently added the following coin to Tantalus:
It isn't in ERIC because the obverse legend: IMP MAXENTIVS DIVO MAXIMIANO PATRI isn't listed as a possibility for Galerius.
It is listed under Maxentius along with the variant ending with SOCERO. As ERIC generally, if not intentionally, lists posthumous coins under the emporer they memorialize, these inscriptions aren't needed for Maxentius. This seems to be the case as there are no coins listed under Maxentius that use them.