The passport was issued by the Tibetan government in 1947, Tenzin Tsundue, general secretary of the Friends of Tibet group, said in a statement.
He told AFP the group knew of no other Tibetan passport that had survived.
The passport a large sheet of traditional Tibetan paper ?was given to then Tibetan Finance Secretary Tsepong Wangchuk Dedhen Shakabpa, who was leading a trade delegation to China, the United States and Britain, it said.
This document stands as an important proof of the independent status of Tibet, legally recognized by other countries before China's invasion of Tibet," he said.
Tsundue said the document had visas issued by a slew of nations such as the United Sates, Britain, India, France, Italy, Switzerland and Egypt.
The passport contains in the center the Tibetan government seal surrounded by seals of different governments that issued visas to the official, he said.
China says its occupation of Tibet liberated it from feudal oppression.
But Tibetan spiritual leader the Dalai Lama who fled Tibet in 1959 during a failed uprising against China's rule and now lives in exile in northern India says Tibet's six million people still suffer repression.
Beijing formally established a Tibetan Autonomous Region in 1965 but the Dalai Lama complains there is no genuine autonomy and has been waging a campaign to press China to provide greater rights to Tibetans.
The passport had been given by Shakabpa to an Indian friend in 1992 and ended up with an antique dealer in Kathmandu, said Tsundue. It was not known how it found its way into the antique dealer's hands. It was bought back for US$10,000 ?borrowed from a Tibetan monastery in 2004.