Haemoglobin literature spectra does not match
As stated by Scott Prahl :


  One of the most confusing things about looking at hemoglobin (Hb)
  spectra is that the values are typically tabulated in equivalents. The
  term equivalent is used to indicate the amount of hemoglobin which
  contains 1 gm atom of Fe and combines with 1 gm molecule of O2 or CO.
  One equivalent of hemoglobin is assumed to be 64,500/4 or 16,125 gm. A
  concentration of 10$^{-6}$ equivalent is 16.125mg of hemoglobin per cc.


It seems that Assendelft and Zijlstra used the equivalent quantification of haemoglobin, meaning that all their extinction coefficients should be multiplied by 4. This leads to the following figure:



Sorry for not having read again Scott Prahl's description before posting. I read it several months ago, as I was gathering data from different source and forgotten it since...