Italian law discourages export of antiquities.
However, it is difficult, perhaps impossible to say for sure where your coin came from and when. The coin may have been found any time in the last 2000 years, and need not have been found within the geographical confines of present-day Italy. The chances are good that it was found in Italy in the last 400 years, but the laws against export of antiquities are of relatively recent date. Many archaeologists take the attitude that all private possession of old things is immoral. Many of them are a little vague on definitions and ground rules, however.