Thats my thoughts to Steinar, I thought it was just interesting looking, and had been fired so as my neighbour had assumed,safe.
the weight of the thing when I picked it up suggested to me it was still packed with something though, and the detonating cap looks super clean so someone either cleaned it well and filled it with gold coins
orits still packed with kapow powder.
I think I will suggest he calls the police on it. I cant find any reference to that detonator/fuze head anywhere on the net if anyone has an idea just what this thing could be.