Walthers HO Nickel Plate Road Dynamometer Car car#X50041 - I found this car in one of my collections - it is used, but is in like new condition - I don't have the box for it - it has metal wheels and knuckle couplers - on one end of the car is a coupler that can be pulled slightly to measure force of some kind - inside the car is a needle that is visible and can be seen moving when the coupler is being pulled - I'm sure some of you know exactly what I'm trying to describe -