At about 924 cm-1 a peak is found in the outer coating, which is not visible in the
coated paper sample. The same seems to be true for the peak at about 1640 cm-1.
However, at close inspection one can see a small peak around 1584 cm-1
(red curve infigure 1), which might be due to the coating. Therefore, the intensity of this peak could be used to measure the thickness of the outer most coating, if a calibration with different coatings of known thickness can be made.