I found this...whatever it is...in the bottom of an old gun cleaning kit I recently picked up. I'm hoping someone here can help me identify what it is.

As you can see in the photos, it's a metal tube, about cigar-size, with knurled caps on each end and a divider inside creating two separate compartments. One side's cap is solid with a rubber seal and a flat-tipped pin attached. The other side's cap has a black rubber or plastic insert. This side's compartment holds the small bronze(?) thing you see. This thing, whatever it is, itself unscrews into two separate parts. This thing also had a foot or so of cord/string attached and wound around it but it basically disintegrated when I was taking it apart. The whole thing was soaked in oil.

What's driving me nuts is I know I've seen something like this before, who knows when or where, but I should know what this is and, for some reason, it's just not coming to me. Even an hour or so on Google was no help. So, anyone have any ideas?