Question About Common Reverse Types On 4th Century Romans

Let's ask a similar question. Imagine you're an archaeologist or coin collector 2000 years in the future. They might wonder, "Why is the design of the American quarter dollar with the eagle on it so much more commonly found than the other quarter designs?" Ultimately, the answer is the same as the answer to your question: "For whatever reason, the coin design remained unchanged for a long time."

Let's take three Roman emperors: Tiberius, Hadrian, and Constantius II. All ruled for quite a long time, by Roman imperial standards. The coins of Tiberius show every little variation - there are basically only two types of denarius. The coins of Hadrian show tremendous variation, with hundreds of different types featured on the denarius. The coins of Constantius II are once again only issued with a few different coin designs. SO length of reign is not the sole determinant of stable coin design.

Uniform, unchanging design of coinage is important if a government wishes to give the appearance of order and stability. The fractured state of the Empire at the time of Constantius II made central control and co-ordination of design important, giving the appearance of unity and co-operation, even if the reality was that the rulers of the various parts of the Empire hated each other's guts.

Countering this is the desire the government might have to use the coinage as "newspapers", telling the people the latest propaganda. Under Hadrian, there were all sorts of "good news" messages the government wished to convey. In the time of Constantius II, there was a general dearth of good news, so the generic "happy days are here again" message was as good as any.

One more thing: It happens that the horseman type came just as the economy was on the skids and weight standards changed frequently (always getting smaller). That meant people hoarded the good old coins in favor of spending the newer, lighter ones and the mints made more and more replacements which would be hoarded away, too. Had the weights not been changing so fast, each individual coin might have circulated longer and more would have been worn out rather than being saved. The coins that survived until today were not the ones that circulated in daily commerce but the ones that got put in a safe place for retrieval later. The original owners never planned for 'later' being 1700 years later.