Twenty four kilograms of coins dating back to the 18th century were found at a private residence in Hai Phong City.
The coins were handed over to the city museum this week, said Do Xuan Trung, the vice-director of the museum.
Nguyen Van Bay was reconstructing a small wooden pier over a pond outside his house in Quoc Tuan Commune, An Lao District, when he found the ancient coins.
Trung said that after cleaning and sorting, they found some of the coins had been minted during the reign of China's Qianlong Emperor while others had been produced by uprising peasants under Vietnam's Le Dynasty in the 18th century.
The coins were packed in a ruddy wave-patterned jar and hidden in the pond. The zinc-bronze doubloons have taken on a dark, rusty color over the years.
Bay's family was rewarded by the museum for their discovery and their willingness to hand it over the museum, according to the vice director.
Trung said the city museum has a vast collection of ancient coins but no archeologist to date and uncover the history behind them. The ancient treasures are gathering dust in the museum for lack of expert care. The newly discovered coins face a similar fate.