Test Weight Car PRR #490387 - HO Scale. Test Weight Cars had known weights so track scales could be precisely calibrated. They were used to check axle load limits and to determine the billing of customers for cargo loads. Bachmann Test Weight Cars come in a variety of colors and road names. Each Test Weight Car fully assembled and features; Highly Detailed Die-Cast Painted Bodies with Separately Applied Brake Wheel and Precision Graphics (where applicable), Blackened Machined Metal Wheels with RP 25 Contours, Magnetically Operated E-Z Mate® Couplers, Non-magnetic Blackened Brass Axles with Needle-point Bearings, and Scale Like Weight for Optimum Tracking Performance.