Bomb disposal experts were called to Darwen town centre over the weekend to deal with an unexploded grenade.
An Army bomb disposal destroyed the suspected World War Two grenade that was handed to police.
The area around the Market Hall was cordoned off after the owner approached officers with it at on Saturday afternoon.
Police said the item had been in the owner's family for a number of years and they had been advised to seek police advice on its safety.
The item was safely moved and destroyed by demolition.