Nice non ferrous weight
as stated above most likely tinned copper.. Nice heavy pieces of tinned copper.
I broke down one of those fuses, the copper bar runs all the way through, but it was full of a white powder. As soon as I noticed that I finished dumping it out inside a sealed bag then very carefully pulled out the bar caps and rivets (all copper on mine) the fuse gave me around 7 lbs of copper if I remember right.
I would not do that again as I am not sure what the filler was... random white powder...yeah I'm all set cut off the ends and be done with it, or maybe someone else knows more on that.