​Black plastic object, full of black powder, nailed to a beam in the attic of a house built in the late 70s

I found this in the attic of the house I recently bought. The opening to the attic in the garage, and this was about an arms length away from the opening in the direction of the rest of the house.

I tried picking it up from the end I could reach, but it seemed stuck. It wasn’t until after I had wiggled the one end free that I realized it had been nailed down.

In doing so I seemed to have cracked the other end where it is still attached to the beam, and when that happened a coarse black grainy substance started to spill out. You can see in one of the photos where it is cracked.

I couldn’t see any discernable markings or logos anywhere on the object.