A woman was walking her dogs through a field when one of them dug up what looked like a potato.
Terri-Jade Barwell put it in her bag and forgot about it, only for her partner to make a shocking discovery.
Her boyfriend, Mark Higgins, said: "I think you need to get out the shower".
He had discovered what a grenade looked like on the internet, and it was the same as what Terri-Jade had found.
When Nottinghamshire Police arrived, officers cordoned off part of the estate in the Cherhill Close and Barbury Drive area, and a bomb squad team was called out to what they said was a "practice bomb".
Nottinghamshire Police said the device was "not highly explosive" but said it did contain a small charge.