Under the parcel shelf - what are the holes?

[scoot]

The carpeted parcel shelf behind the seats -- if you take out the wood boxes and look at the floor you see what looks like a 5" round inspection hole - one on each side of the car.  They are each held in by 3 or 4 screws.   But when you take them off, it is unclear what they are there for.  I can't figure out anything to inspect or adjust using these access holes....    Can someone enlighten me?

[scoot]

OK, in case anyone want to know what they are, I finally figured it out.  They are in Group 68 and are called "Cover for immersion paint holes".  There are two of them, part number 113 683 01 10.  There is the associated seal washer part number 113 997 0041.   Found this through my recently purchased MB 230 SL Spare Parts List (I think it's the dealer edition - 10 097 -- wonderful book).