I just saw this rare type for sale, but it seems a bit pricey at $960.00. It is listed as a silver denomination in RIC, but this one looks bronze with some silvering.
Seller's description-
Constantius Chlorus - Argenteus
296-298, Chartago, RIC 14a
2,47g x 18mm
D/ CONSTAN - TIVS CAES; testa laureata.
R/ F ADVE - NT AVGG NN; T (esergo); l'Africa con uno stendardo e una zanna di elefante; in basso, un leone e un cranio di bue.