It seems like the whole unit is glued together, so I am hesitant to try and pry it apart. When looking through the hole where the light bulb goes, it seems quite clean.
It might be some loss of reflective coating.
I recently bought a beautiful D2 (facelift 2003), but just noticed a colour difference in the rear lights. Is someone able to confirm that this is odd? The right side is chipped just a little bit, so I might want to replace that with an identical...