Diocletian (284-305) can rightfully be called the best organizer of the Roman Empire since Emperor Augustus (27 BC-14 AD). Both introduced reforms which set the standards for ages to come.
Along with several political and military improvements, Diocletian also reformed the Roman currency system. In doing so he introduced new denominations, among them small coins like this one. Unfortunately it is unknown to us how the Romans called these bronze coins. Modern collectors refer to them as nummi or folli.