RIC V Pt. 2 515 has two quite distinct descriptions (entry attached below) - "Hercules stg., looking l., or walking r., holding club, trophy and lion's skin". I have been able to find quite a few examples of the standing type which would be described more accurately as "Hercules standing facing, head left, holding trophy, club and lion skin". Is the walking right type, which I believe would be the description of my (addmittedly poor) example below scarcer or am I simply not looking hard enough? Obv:– IMP MAXIMIANVS P F AVG, Radiate, draped and cuirassed bust right Rev:– VIRTVS AVGG, Hercules walking right, trophy over left shoulder, lion's skin draped over left arm, holding club in right hand Minted in Rome (//XXIS). Reference:– RIC V Pt. 2 515 Bust Type F.
I don't have any hoard data or anything, but I agree with you that in the marketplace, the Hercules walking right types come up less frequently for sale.