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. Of course, anyone who truly loves antiquity deplores the looting of archaeological sites and the resultant loss of information. The most successful method of preserving antiquities becomes an effective failure, however, if that which can be learned from them is bottled up in academia, and lay people are discouraged from anything more than a passing glance at our history. We are all heirs, and we all stand to learn from the past. The U.K. has the most enlightened approach and the greatest success, by far.