From the press release:
Affalterbach. It doesn’t get any better: with victory in the constructors’ world championship as well as the drivers’ championship plus runner-up titles clocked up by Lewis Hamilton and Nico Rosberg, the MERCEDES AMG PETRONAS Formula One Team has achieved the ultimate in motorsport’s champion’s league in 2015. To mark the end of the season Mercedes-AMG is celebrating this outstanding team achievement with an exclusive special model: the MERCEDES AMG PETRONAS 2015 World Champion Edition of the A 45 4MATIC blends the expressive Formula 1 look of the victorious Silver Arrows with particularly extensive and unique equipment.
Photos and press release - Special edition Mercedes-AMG A 45 4MATIC For F1 double triumph