The metal device was put in a mop bucket inside a wheelie bin
Bomb disposal teams and police cordoned off a home in Greater Manchester after reports of a WWII landmine - only for it to turn out to be an engine part.
Michael and Andrew Lysaght discovered the chunk of metal, which had a spiral pattern etched in it, at Park Bridge Heritage Centre in Ashton-under-Lyne.
They took it back to their parents' house and found a similar device on an ammunitions site on the internet.
Police were called and x-rays were carried out on the piece of metal.
Michael Lysaght, who had been taking photographs of the various artefacts in the park, said his whole family became "pretty scared" when they thought it might have been an unexploded landmine.
"We couldn't believe it when we saw a similar picture with the heading WWII landmine.
"My mum wasn't too pleased with us, she wasn't too happy that we had brought something back that could potentially destroy her house.
"We put it in the back garden and called the police, at first I don't think they took us seriously."
However, when officers arrived at the family home in Chadderton they put the potential explosive in a mop bucket in a wheelie bin and called the bomb disposal team in Chester.
Andrew and Michael Lysaght were told to leave the property
Mobile phone pictures were sent to the bomb experts, a team arrived within the hour and the Lysaght family were not allowed back in their home.
Mr Lysaght said: "They then began to take it more seriously and the bomb disposal team carried out investigations and x-rayed our discovery."
After three hours they finally gave the all clear, and the cordon was lifted.
"We were very relieved, but we are still puzzled that the teams took the metal device with them - if it wasn't dangerous why did they take it?"
A police spokeswoman confirmed an area had been cordoned off and the bomb disposal team did attend.
"After a series of checks it was found to be an old engine part," she added.