First, there is no unification? Mold? Unlike RMB today, roller coasters are mass-produced, so they can be produced. Mold? People took advantage of this. This roller is unique in the world, only one. Most people have never seen it in their lives, and they have no chance to get in touch with this kind of thing, so how can they imitate it? The production of the tiger charm, with many words and lines on it, is a very complicated and precise thing on the whole. It's not just a simple metal object being split in half.
If people want to copy, they must know what is on the tiger symbol to be copied. Just like today, if people want to copy dollars, they must know what patterns are on the dollars and in what order they are arranged and combined. So the tiger symbol wants to be copied into one? Small-scale events? In other words, only people who have access to the drum can copy it. But not to mention the difficulty of copying the tiger symbol, no one wants to take the risk. If you work hard to create a tiger symbol and lose your mind just because the small differences in one place can't match, it's not fun at all.
Second, there is no need to imitate. In fact, people pay too much attention to the fact that road rollers can mobilize the three armed forces. In real life, the mere existence of the tiger symbol may not mobilize the three armed forces, but also depends on who has the tiger symbol! In other words, a common man with a flat head holding a tiger symbol will not mobilize the three armed forces, but will be beheaded as a usurper. Generally speaking, people who have the right and status to hold tiger charms are prized by the emperor, at least in the military camp. Otherwise, you can't even get into the camp!
In this way, there is absolutely no need to imitate the roller. After all, even if the roller is made, where can a living person make it? Finally, even if the three armed forces are really mobilized, as long as the emperor appears, all of them are useless, and the finally mobilized three armed forces will immediately obey the emperor's orders and ignore the tiger symbol.