Roman Sestertius

The Roman sestertius was the empire's workhorse for propaganda, plastering emperors' portraits on a coin that circulated from Britain to the Euphrates.

Weighing between 25 and 35 grams and measuring up to 35 millimeters across, it was struck from brass alloys that included zinc and copper. Minting occurred mainly in Rome, though exact production techniques varied by reign. For instance, under Septimius Severus, dies were engraved with finer details to highlight military triumphs.

Records of exact mintages are spotty; much was lost when the imperial archives decayed over centuries. That said, archaeological digs turn up thousands, suggesting they were churned out in vast numbers for soldiers' pay and trade.

One oddity: the sestertius's large flan sometimes led to off-center strikes, as if the minters were in a hurry. Not that they'd admit it.