Trying to secure its claim to treasure worth $500 million, Odyssey Marine Exploration argued Tuesday that Spain has no right to 594,000 mostly silver coins the Tampa deep sea salvager rescued from the ocean floor in 2007. Odyssey was responding to a federal judge's June recommendation that the treasure is the sovereign property of Spain. The treasure ship was probably the Spanish frigate Nuestra Senora de las Mercedes, sunk by a British squadron in international waters off Portugal in 1804. In court papers filed Tuesday, Odyssey insisted that since most of the precious cargo belonged to private parties that hired the Mercedes as a commercial transport, the Spanish government has no right to the loot, the company said. Odyssey is the world's only publicly traded undersea treasure company. The Mercedes hoard is locked in a Central Florida vault pending resolution of lawsuits.