Bernardo Viera Trejo still remembers that 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 the island's dictator, Fulgencio Batista, with an assault on the Moncada military barracks in southeastern Cuba. He had failed and spent the last two years behind bars. As the two chatted, Viera says Castro drew a map of the doomed attack and signed it for his friend with a flourish.

Now, more than half a century later, Viera is selling the map through the Dallas-based Heritage Auction Galleries, the latest in Cuba-related historical documents placed on the auction block.

''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 the attack was significant but had no idea Castro would become the island's leader, let alone rule the country for so long. Days after their meeting, Viera left for Europe as journalist for the Spanish magazine Bohemia. Castro fled to Mexico where he prepared another coup against Batista.

When Castro returned to Cuba in 1959, Viera rushed to write about his revolutionary efforts. But like many early supporters, he soon became disillusioned with the new government's frequent executions, the arrival of Soviet advisers and the attacks on the same press that had heralded Castro's arrival.

Viera fled to Venezuela, eventually settling in Miami. He says he is auctioning the map because of its historic value and because he needs the money. The idea came to him after he read about a similar auction Heritage held for a lock of hair snipped from Ernesto ''Che'' Guevara before his burial in 1967. A Houston-area bookstore owner paid $100,000 for the lock in October.

Jaime Suchlicki, head of the University of Miami's Institute for Cuban and Cuban-American Studies, dismissed the notion that Castro's ailing health has triggered an upsurge in Cuban memorabilia sales. He questioned the map's authenticity, adding, "There's always people selling stuff. People are still selling things from Hitler.''

Sandra Palomino, of the Dallas-based Heritage Gallery, which plans to auction the map Thursday, said she is convinced Castro's signature is authentic because it matches other verified examples of his signature from that time and because 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.''