Police were called to New Mills on Saturday after a suspected grenade was found on a canal barge.
A police cordon was put in place and anyone within 100 metres of the scene was asked to evacuate while the Army’s Explosive Ordnance Disposal Team (EOD) examined the item.
After a thorough inspection, EOD determined the grenade to be safe and the police cordon was removed.
Officers urged people to always call 999 if they find an item resembling an explosive.
A police spokesman said: "Thank you to all members of the public who spoke to our officers on the cordon for their understanding and we apologise for any disturbance caused.
"It is common for families of war veterans to find these unexpected souvenirs. A lot of service members either bought them home from the war or purchased them later.
"However, devices like the one below can remain intact for decades and explode without notice."
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