What is the name of this high-performance version of the 6 series coupe/ convertible, which appeared on the Moscow BMW billboard?
Moscow BMW billboard: The Moscow BMW billboard was unveiled in 2008 as one of the largest and most elaborate billboards in the world. Moscow BMW billboard:  The car models on the billboard were the BMW M Coupe, the BMW M3, the BMW M5, and BMW M6. BMW M6: The BMW M6 is a high-performance version of the 6 Series coupe/convertible, designed by the motorsport division of BMW.
BMW M6