The Treasure Act 1996 requires reporting discoveries of antique gold or silver coins and objects in the UK.
Finds must be reported within 14 days to the local coroner, or to the Receiver of Wreck for underwater discoveries.
Prompt reporting allows researchers to study finds in their archaeological context, which is lost if illegally kept.
Museums can purchase reported treasures at fair market value for public display and education.
Police arrested 2 men for violating the Act after 300 Civil War era coins were found on a Herefordshire farm.
Authorities say anyone possessing such coins from discoveries can safely return them without penalty.
It follows a 2019 case of 2 men convicted for concealing a £3 million Viking hoard also found in Herefordshire.