Walking weight
Found whatever this walking along the rail tracks
Any idea ???? Maybe part of a train brake system 
Discussion
intriguing. I don't think its part of the brake system. maybe related to manual switch throw? any markings on it?
No markings but another angle of it.
There is a large keyway on cylindrical end 
Looks like a wedge used to force tracks one way or the other where they split, so the train can continue on the right track.