One of the rarest and most valuable British coins in existence ... government to introduce cheap metals into coins previously made of sterling silver - known as the Great Debasement.

Several dozen other coins, made of an alloy of gold, silver and copper, come from what is now Great Britain and were stamped ...

A hoard of silver coins discovered in a County ... 10% precious metal for it to be declared treasure. The coins will now go to the British Museum for valuation and should eventually be acquired ...