Spanish cultural officials have allowed a first peek at some of the 14.5 tonnes of shipwreck treasure worth about US$500 million (NZ$609m) that a United States salvage company gave up this year after a five-year ownership dispute.

Only a tiny portion of the haul from the Nuestra Senora de las Mercedes, a galleon that sank off Portugal's Atlantic coast near the Strait of Gibraltar in 1804, was shown to the media last week: 12 individual silver coins, a block of encrusted silver coins stuck together after centuries underwater, two gold tobacco boxes and a bronze pulley.

Authorities who have been inventorying the treasure since it was flown from Florida to Spain in February said it will be transferred later this year from Madrid to the National Museum of Underwater Archaeology in the Mediterranean city of Cartagena. Displays are expected to start next year.

Though previous estimates have put the value of the treasure at US$500m, Spanish officials said they were not trying to determine an amount because the haul is part of the nation's cultural heritage and can never be sold under Spanish law.

Spain took possession of the treasure after courts rejected arguments that Florida-based Odyssey Marine Exploration was entitled to all or most of the treasure.

The inventory counted 574,553 silver coins and 212 gold coins.

The metals were mined and the coins minted in the Andes, from places that are now in Bolivia, Chile and Peru.

Spain overcame an effort by the Peruvian government to block the transfer of the treasure back to Spain.

Peru did not gain its independence until 1824, but lawyers argued it was more than a simple colony at the time because it was the local seat of the Spanish crown when the ship sank.

- AP