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.