The 600-year-old gold ducat was spotted on Loe Bar beach back in 1996 by a couple walking their dog.
Loe Bar is half-mile long shingle shore near Helston in south west Cornwall with the surrounding waters having a long-held reputation for powerful waves and treacherous currents. It is believed that the coin could have come from one of the numerous shipwrecks that occurred around the Lizard peninsula over the centuries.
The coin itself dates from the reign of Ferdinand I (1380-1416), the King of Aragon who was also ruler of Sicily and Sardinia. It carries the mark of Giancarlo Tramontano, the last mintmaster appointed to Naples by the Argonese rulers.
Measuring 22mm in diameter, the coin has been consigned to Barbara Kirk Auction’s sale in Penzance on January 17 by a relative of the original finders.
It will be estimated at £500-800.