The Transfomer Car No. 6518 was produced on a die-cast chassis that was designed for the Girder Bridge Car No. 6418 except that two holes are drilled in the chassis to hold the transformer.
The transformer is different from those that were used on the No. 2461 Transformer Car in that it is not painted. Instead it uses injected molded BLACK plastic. There are also raised plates at the bottom and the top on the sides of these transformers. These plates were heat-stamped in WHITE on the top "LIONEL / TRANSFORMER / CAR," and the plate at the bottom indicates the number "6518." Also, the insulators on the transformer are a more translucent WHITE color. These insulators on top of the transformer are easily broken.
There is no number on the sides of the chassis. Beginning in 1956, Lionel would put this inscription on the bottom of this car, "Machinery Car Part #6418-4" with the actual production number shifted to the transformer load. This car was not produced after 1958 and came with bar-end trucks that have tabbed couplers, there are two variations:
Variation A: Lighter GRAY painted chassis.
Variation B: Darker GRAY semi-gloss finished chassis.
Note: Due to the size of this car it will only operate of O Gauge track, and even then, the overhang is such that I would recommend that it be used on 072 Curved Sections of track.