A treasure trove of 80 American gold coins has been unearthed in a Brisith garden, it was revealed yesterday.

The hoard of “Double Eagle” $20 pieces, dating from 1854 to 1913, were discovered in Hackney, east London.

It is not unheard of for buried money from Roman times to be found, but the 19th and 20th century US coins have intrigued experts, who estimate they could be worth up to a six-figure sum.

Roger Bland, head of portable antiquities and treasure at the British Museum, said: “It’s a unique discovery, nothing like this has been found before. There is a fascinating story behind it, but we don’t understand what it is.

“It’s a mystery who put them in the ground, how they got hold of them and why they never came back to collect them.”

The high denomination coins were minted at various US locations including San Francisco, Philadelphia, Denver and Carson City.

A search has begun to trace the coins’ owners or ancestors as preparations are made for the collection to go on display tomorrow at the British Museum.The Museum of London was initially alerted to the find by four people.

An inquest was opened yesterday at St Pancras Coroner’s Court by Andrew Scott Reid in which the find was officially announced.

The owner has until February 8 next year to come forward. Details of exactly where the coins were discovered and by whom are not being disclosed to discourage any false claims.

If no claim is made the coins could qualify as treasure under the terms of the Treasure Act 1996 and become property of the Crown.

Hackney Museum has expressed an interest in purchasing the hoard, which would then be costed by the Treasure Valuation Committee. Any money paid would be divided between the owner of the land and the finders.