The historic item was washed up on Gress Beach on the Isle of Lewis this morning.
The coastguard were alerted to the discovery and police and disposal teams were sent to deal with it.
A cordon has been erected and police asked the public to stay away from the area while the small device is disposed of.
A force spokesman said: "A small item which appears to be unexploded ordinance has been recovered on the beach.
"Police will maintain the cordon until the item has been safely disposed of and request members of the public to stay away from the area."
It follows the discovery of a suspected mortar bomb on a beach in Norfolk yesterday.
Bomb disposal experts carried out a controlled explosion on the seafront at the village of Hemsby after it was discovered by a member of the public.