In Call of Duty: World at War the vehicle is untextured, crudely modelled and shaped like a typical modern automobile. It has exhaust pipes, six wheels and a spoiler. The vehicle differs from a normal car simply because it's armed with World War II-era weaponry.
In Call of Duty: Modern Warfare 2 the vehicle appears almost insect-like, with no wheels or any resemblance at all to any conventional vehicle. The appendage at the top was most likely used for turret testing.
The vehicle in Call of Duty: Modern Warfare (2019) differs slightly to the version featured in Call of Duty: World at War as it is wrapped in a crude bright pink texture with it having the words 'Do not Use' written on it, something that is more clearly seen on the vehicle's hood. Something that does set this vehicle part from the others is the fact that it can be viewed in-game through using the free-cam tool (in Spectator Mode) on the external areas of the Atlas Superstore map; there are multiple iterations of this spread around, with two of the prominent being featured in front of the Dam location nearby.