Visually, there is no difference at all that I can tell. Same with smoothness, it's as smooth as the rest of the car. Presume it hadn't been in an accident, then what in the world could be the reasoning for the hollowness or the different covering (door worked on before?) ??
I suppose it's possible that the skin of the door was replaced after an accident, that could/would explain hollowness sound in SOME way? Agghh, I'm confusing myself!
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)