One of the most interesting aspects of Greek coin design is the development of the reverse designs. This evolution reflects how quickly the Greeks mastered the die making and metallurgical processes involved. Whereas the coins of the Romans and other empires were minted on a national basis, Greek coins were minted by numerous city states. The competition, both in artistic impression and to have a city's coinage accepted widely, probably drove this process. The quality of the coinage became a reflection of the city's status. The technology and art seemed to develop faster in the Greek colonies of Magna Graecia In the chart below, the coin of Metapontum, which is an incuse representation of the obverse design, and the Syracuse 16 litrae coin stand out as more advanced than the other coins of Ionia and mainland Greece. The dates given for each coin are approximate and the production of many of these overlapped.