Early American coins
The 8 reales also known as the Spanish Milled Dollar was legal tender in the United States until the Coinage Act of1857. The original United States silver dollar was based on these coins.
Ancient Greek coins
The early coins of Magna Graecia were very different than other ancient Greek coins. The coins were minted with an incuse technique, the same central image in relief on the obverse and aligned in negative on the reverse. It has been speculated that Pythagoras who died at Metapontion in 500 BC devised this feature “an attempt to realize in concrete form a confrontation of opposites that was characteristic of the Pythagorean system of thought” (Rutter 1997,
Ancient Roman Imperatorial coins