Well I just looked at the CLK (2001) and could not find a VIN # on any body panel, or anywhere where on the CLK that they'd be on my car... Interesting...
Now I'm not sure if your car has them... I will have to look at another Mercedes and see if this is normal. Now this makes me curious if my MB is the only one with this...
Well I will tell you where they are on my car. On each door, they are on the front side of the door... this is hard to explain. The rear doors VIN numbers are closest to the B pillar and you can only see them if the door is wide open. Same with the front doors only to the A-Pillar.
As for the bumpers, they are on the bottom of them, you have to look from below the car, up at the bumpers to see them.
For the trunk, it's on the inside of the trunk lid where it meets the rear window. And the quarter panels are in the drains on top of the trunk (left and right), trunk must be open to view them.
And as for the front quarter panels and the hood, I believe it's similar to the trunk explanation.
I hope you can find them, if you can't, then the way Mercedes did it must have changed over the years. Anyway, HTH, and keep us posted.
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!)