Close to 50 pounds, nice grip, grove & slot in the bottom to ride on - what?
Probably industrial equipment of some sort. Is it exactly 50 pounds? then it would be for calibration. But that base looks like it's meant to be slid up and down a rail to balance something.
Scale of some sort?
Bug smasher!!
Extreme duty door stop. Bob
A guy on yesterdays tractors has some just like it, marked "Otis Elevator" Test weight for the elevator people.