Keizer:AUGUSTUS. jaar:27 BC-14 AD. munt soor:Æ Sestertius gewicht; 33 mm , 21,8 g Stad;Rome mint. Struck 16 BC. keerzijde:Ti. Sempronius Graccus, moneyer. keerzijde: Legend in three lines within oak-wreath flanked by two laurel branches reacties zijn welkom, is leerzaam / Large S C; countermarks: radiate head right and Lunar goddess(?) standing left.
As far as the countermarks go, the standing figure has been described as "Helios standing left," and "head of Helios or gladiator helmet." These two marks are found on the larger bronzes of Augustus and are conjectured to be of Sicilian origin. Compare your coins to these sestertii... Source