The Salvation Army of Palm Beach County said the workers were sorting through a box of donations when they stumbled upon the grenade, which still had its pin, the South Florida Sun Sentinel reported Tuesday.
A police bomb squad investigated the item and determined it was inactive and may have been manufactured during World War II.
"That was the most unique item that has been discovered," said Tara Holcomb, development and public relations director for the Salvation Army.
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