Airbag colour/texture is the other big risk. You have leather airbags and plastic ones - the textures being different, and the colour codes being different between different models etc etc. Sometimes Mercedes put plastic airbags with leather wheels (if they have a rough texture), they seem to put leather ones on cars with wood/leather wheels, etc
Ive been looking at the SL/CLK/E-facelift and i've found 21 different colour/leather combinations across those airbags that look physically the same.
And airbags are expensive ... more than the wheels ..