A collection of 37,895 Spanish coins including rare examples from the 15th century went on display in New York for an auction organised by Sotheby’s next month.

The collection also includes a copy of the Ides of March denarius... coined by the ancient Roman politician Brutus in the year 4BC to commemorate the assassination of Julius Caesar

The collection includes coins from antiquity through modern era and feature the only remaining example of Europe’s most famous coin, called 50 Excelentes, commissioned by the 15th century monarchs Ferdinand and Isabella as gifts.

The coins are part from the Archer M. Huntington collection and valued between $25 million and $35 million (circa €19 million and €26.5 million). They will be sold in a single batch in a sealed bid auction that ends on March 8.

The collection was put together a century ago by American railroad magnate and philanthropist Archer Milton Huntington, who also founded the Hispanic Society of America.

“We put the entire collection on view,” said David Redden, Sotheby’s vice chairman and head of special projects. “It starts nearly from the beginning of coinage in the Iberian Peninsula.”

The collection, which is owned by the New York chapter of the Hispanic Society of America, was offered to the government of Spain before the auction but its bid was too low, Mr Redden said.

“This is not an easy time for Spain,” he said. “Nobody said, ‘no,’ but nobody is actually coming up with the money.” Persons who have expressed an interest in the auction include Americans, Spaniards and other Europeans, he said.

The collection is dominated by the nearly 140g solid gold 50 Excelente coin, which Mr Redden called “arguably the most important and valuable European coin in existence”.

It shows a profile of the monarchs on one side and a shield on the other side. Other 50 Excelente coins were minted but disappeared for reasons that can only be guessed.

“Such a large piece of gold, it’s attractive to try to melt it, unfortunately,” he said.

The collection also includes a copy of the Ides of March denarius, which was coined by the ancient Roman politician Brutus in the year 4BC to commemorate the assassination of Julius Caesar, in which Brutus conspired. Other coins in the collection were among the first minted in the New World as the Spanish colonised the Americas and coins from the Muslim period in Spain.

The coin collection is on display at Sotheby’s New York galleries.