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Bernardo Viera Trejo still remembers the sweltering summer day in 1955 when he and his then-friend Fidel Castro met up shortly after the would-be revolutionary's release from prison.

Castro had attempted to overthrow Cuban dictator Fulgencio Batista with an assault on a military barracks. The attack failed and Castro had spent two years behind bars. Viera says that while they chatted, Castro drew a map of the doomed attack and signed it for him with a flourish.

Viera is putting the map up for auction this Thursday at Heritage Auction Galleries in Dallas.

"I believed he was an important person and would become even more so," said Viera, a former journalist who has interviewed luminaries including Ernest Hemingway and Argentinean writer Jorge Luis Borges. "But Fidel, he couldn't understand why I wanted it."

Viera, 75, believed at the time that the attack on the Moncada military barracks was significant even though Castro was then still far from becoming the island's leader. He left for Europe as a journalist for the Spanish-language Cuban magazine Bohemia. Castro fled to Mexico to prepare another coup against Batista.

After Castro won power, Viera like many early supporters soon became disillusioned with the new government's frequent executions, Soviet advisers and attacks on the same press that had heralded Castro's arrival.

Viera eventually settled in Miami. He says he is auctioning the map because of its historic value and because he needs the money. He had read about a similar auction Heritage held for a lock of hair snipped from Castro ally Ernesto "Che" Guevara before his burial in 1967. That lock of hair brought $100,000 in October.

Jaime Suchlicki, head of the University of Miami's Institute for Cuban and Cuban-American Studies, questioned the map's authenticity.

"There's always people selling stuff. People are still selling things from Hitler," Suchlicki said.

Sandra Palomino, a representative of the auction house, said she is convinced Castro's signature is authentic because it matches other verified examples of his signature from that time. Also, it was first published in a book printed in Cuba not long after Castro took over.

"Regardless of what your feelings are, his autograph is highly desired," Palomino said. "He's an important historical figure."