A hoard of 80 gold coins from the US has been discovered in an east London garden.
The coins, found in Hackney, were minted between 1854 and 1913 and are estimated to be worth a six-figure sum.
While Roman coins are often found buried, it remains a mystery why the American hoard was hidden.
An inquest at St Pancras Coroner's Court announced the find and set a deadline of 8 February 2011 for the coins' owner to come forward.
Details of how and where they were found are being kept secret to prevent false claims.
If nobody claims the coins they could be declared as treasure and become the property of the Crown.
The coins are due to go on display at the British Museum in central London on Tuesday.
Dr Roger Bland, head of portable antiquities and treasure at the 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."