I would like to introduce you to one of the longest-lived coin types. The item is from that longest-lived civilization - China. The story goes like this:
Towards the end of the Zhou dynasty in the third century BC there were attempts being made to unify the country. When we think "dynasty" we tend to think there is some power principle involved. But that was not the case with the Zhou emperors, who had power, if at all, only within their personal domains. The rest of China was divided between various princes who would bow to the Zhou emperor and send him a trinket or two by way of token tribute, but who otherwise went their own way, which, most of the time, involved internecine war.
By that third century BC the wars had eliminated a number of smaller players, and the bigger ones were starting to think about the possibility of taking the whole ball of wax. This was briefly achieved by two princes in succession, one of who established a new imperial dynasty, the Qin. This was Qin Shi Huangdi. He is famous these days as the emperor who ordered the terra cotta army to be made and interred with him in his tomb. To us numismatists he has become equally famous as the author of a coinage reform that introduced round coins to China.
And, actually, this is not correct. The coins in question, called "ban liang," or "half ounce," were actually made as much as 50 or more years before the triumph of Qin Shi in 221 BC, but they were cast during his reign, and after.
Qin Shi tried to operate a totalitarian state. However, like most such states it went bankrupt, the people revolted, and it broke up after fifteen years to be replaced by the more reasonable Han dynasty. The ban liang continued to be cast during the first Han century, but there was a problem. Ban liangs had been circulating for perhaps 250 years and the minting procedures had been chaotic. Sometimes the law stated that only the central government could cast the coins. At other times, anyone could. The coins came in all sizes and weights, from a full 16 grams down to less than 1. All of them bore the legend "ban liang," or half ounce. Under the circumstances, commerce had to be mediated by the universal use of scales.
In 118 BC the Han emperor Wu Di resolved to do something about this problem. After a few experiments with token coinage he resolved on a new design: the "wu zhu." That translates to 5 zhu, a zhu being the weight of 100 millet seeds. They were handsome coins, with rims and careful quality control. They caught on more or less immediately, driving everything else out of the market.
Wu zhu were then made exclusively until the reign of the usurper Wang Mang, 7-25 AD. Wang Mang made a number of different coins, all of which had a bad effect on the economy. It is now thought that he had some wu zhu cast as well. But on his demise, and with the reestablishment of the Han, the wu zhu returned in force, and continued to be made even after the fall of the Han for another 500 years. Minting was definitively ended with the advent of the Tang dynasty in 618 AD. Wu zhu was minted from 118 BC to 618 AD. That is 736 years, the longest run for any coin ever.
Obverse and reverse view of an example of Wu Zhu.