This is a New York Central prototype traveling gantry crane kit with revolving wheels.  These cranes could move on their own rails straddling several tracks and the winch house enabled the operator to transfer loads from one railroad car to another, or onto a truck, or vice versa. They were used industrially or in lumber or beam yards.  Any flat rail yard should have one.  All parts are precut as much as possible.  Footprint is 10” x 12”.  Height is 10 ¾”.