A museum prompted a bomb scare after unearthing a box labelled "bomb" in its archive.
Volunteers at Bishop Bonner's cottage in Dereham, Norfolk, found the package, filed under the letter "B", while sorting through items held in storage.
They found three clay balls packed with gunpowder with wicks sticking out of them, and Bob Davies, vice-chairman of the Dereham Antiquarian Society, took them home with him.
He said: "I thought they had sat on a shelf safely for 90 years so it should be OK to take them home for safekeeping. I called the police and they told me not to touch them."
"The next thing I knew, bomb disposal experts arrived. I think my neighbours were quite surprised."
A new home will be found for the grenades in the bomb disposal unit's museum in Colchester, Essex.