He created a new coin

Diocletian introduced several financial reforms in addition to his domestic ones. One of the interesting facts about Diocletian is that he restored the use of silver and gold coins and produced a new sort of everyday bronze coin. By the reign of Gallienus (AD 253-268), little any precious metal was left in Rome's silver currency due to years of steadily declining quality. The famed Emperor Aurelian had made an effort to restore the currency, but the citizens of Rome still lacked the superior silver coins that their forebears had received. This would alter Diocletian's reforms. Diocletian boosted the production of coinage, which may have made them worthless, but he also issued laws regulating salaries and establishing maximum prices for certain goods to fight this.

Besides, Diocletian issued a decree setting a cap on the price at which commodities might be sold, with harsh penalties for violators. He doubled the weight of the gold aureus and revalued the currency, producing a new silver coin called the Argenteus. The follis, a brand-new, large billon coin, was also introduced by Diocletian. These, however, were released in far too vast a quantity in comparison to the silver, which had an impact on the reforms and reduced their success. Those regulations were eventually repealed because there wasn't a means to enforce them.