Modern torpedo's (Mark 48) need to have 3 things in order to arm. I seem to remember that it is a minimum forward G force (3?)and electrical charge (wire guided weapon) and I forget the third. Hey I was an A ganger on fast attacks ten years ago, what the heck do I know.
Course you could always place a charge next to the war head and that would pretty much negate the fail safe's. But the weapon would obviously appear tampered with. Though I think a Mark 48 weighs a lot more than 800 lbs. Closer to 4000lbs and the warhead was 670Lbs (or so) of PBX. It could be an old mk 37 exercise weapon (all the electronics and guidance packages, but a dummy warhead) the was a much smaller weapon.
re: "800 lb torpedo..."
I guess that it's only of academic interest at this point, but the "800 lbs" surely refers to the warhead, not the gross weight. To my knowledge, the only torpedo (any flag) that had an 800 lb warhead was the USofA WWII era Mark 8 Mod 4 fish.
Me thinks a keepsake belonging to an old sailor with an understanding wife...