Silver Roman coins weren't just dropped at random in the open fields. If one finds three Roman denarii in the same day, it means he was using his metal detector on an ancient settlement were many coins have been buried among rubble, or on a necropolis of which very few remains except metallic objects (like silver coins, in the deceased' mouth). And he knows it, because there must be many pottery sherds on the surface. He partially destroyed this archaeological site by removing everything metallic, leaving only ceramic material, just for his own selfish individual profit. This is called looting, not more not less.
Gino, first, I found these denarii on the fields that are NOT under National Heritage, and they are NOT under State protection, second, I always ask the farmers permission, and third, I found these three denarii on two different fields...