We had a similar one here in the 80's. A local diver had retrieved a pair of 3-4" shells from a popular local WW1 wreck and was using them an ANDIRONS at his fireplace. One of his neighbors got upset and called the police, who called the bomb squad, and the arguments stopped when the bomb squad was able to detonate the shells without any problems.
But the record
probably goes to E.I.DuPont & company, who took a revolutionary war cannonball (filled with their powder, most likely) that was retreived from a mudbank around that same time. 200 years old, black powder, and it detonated just fine.
Fun stuff, munitions. Sometimes they even do what they're supposed to do. Explode!