I thought I remember reading somewhere that the laquer had effectively powdered glass within it..
This gave it a harder / tougher finish.
The E320 (w211 late 2007) I used to have had noticeably tougher paint than any other merc I have owned..
Just searched the web and have read the following:
"Mercedes holds a record for being a prototype user of this paint in their The E, S, CL, SL and SLK-Class model series. The ceramic particles in the paint form a dense and even structured network which provides greater resistance to any scratches on its surface".