Gordon, it may be possible that it is a one-off made only for the Maharaja. In that case don't you think that the present owner would emphasize more on it as it would add more exclusivity to the already exclusive car, as he had mentioned himself that only 6 were built by Mercedes Benz.
In the link you provided it is clearly mentioned that the 680 S has the body work by Jaques Saoutchik which makes it rare and adds more value to it. Similarly, if the body work of this Mercedes was done by someone else, it would have been called a Mercedes-Benz 680 S ______ . Further it is mentioned in the link that the Saoutchik design took advantage of the Type 680's low slung chassis. The car looks low in the picture as well. When you see the pictures in the link that Ishan has provided as well as the one that I have posted of the 680 S, even they are low whereas this 680 K is quite high.
I am not able to find a single piece of evidence that there was ever a 680K built.
__________________
Ability is nothing without opportunity - Napoleon Bonaparte |