Its alittle older than i first thought,also just a hunch but Its very likely the new rings supplied from brabus will be of a higher quality than the ones first fitted!
Im not too clued up on how strong the bottom ends are or what the main differences are with the 103/104,brabus must have done it for a good reason!.It will be interesting to see what the ring lands are like,and judging by the purple colour you mentioned Jay could be right about the lean mixtures cooking the rings over time.

I agree with your old mercedes dude!,The OE Mahle Mercedes pistons used in the M111/104 etc are very nice,and i admit i was very wrong for once thinking a forged piston could do a better job at the horspower im running!.

As a comparison to the wear you have heres one of my M111 psitons with 100k km's on it,from the wear notice the skirt wall has a concave shape unlike other flat tappered skirts,also there is no wear around the ring area at all!