Well, It would be a grand idea to have your trophy checked by someone who knows about Odnance disposal, and rendering munitions safe. You have said that the device has been defused, did they go so far as to remove the explosives from it? Removing only the fuse, leaves the shaped charge in place, removing the initiator only leaves the fuse, and charge in place. If it is determined to be completely inert, do what you like with it, (in accordance with the laws of your Nation, and region of course) however, if you have a device still holding its explosive charge, it needs to go to the moors for disposal.
My training, and experience in EOD is not extensive, and certainly not current, but a shaped charge is far more dangerous than a smoke, or flare cartridge.(which are still nothing to sneeze at) and fillings used in those days tend to become very unstable with age. I would recommend strongly that despite its history as a war trophy from your G’Dad, it is much too dangerous to have around, and should go to the local EOD people for checking, and if need be, disposal. Call whoever you need to, and do it today. I’ve been to a mop up after someone picked up an unexploded device because it didn’t go off when it hit ground. (it had just not gone off the FIRST time it hit the ground.) 2 dead, several others injured. Not something you want to come home to.
