Just a thought. My 737-300 manual states that the "MAX" CSD oil temp is 157 degrees C. The 'IN' scale give the inlet temp and the 'RISE' scale gives the rise in temp as the oil passes through the CSD. Adding these two together would give you the oil temp as it leaves the CSD. Looking at the gauge closely, you could say that the begining of the amber band on the 'IN' scale is at 137 degrees C. Adding the max 'RISE' of 20 degrees gives you a total of 157 degrees C as it leaves the CSD. I beleive that the reason for the amber band on the 'IN' scale is that it warns to check the 'RISE' if the 'IN' temp is over 137 degrees C. If the 'RISE' is at the max of 20 degrees and the 'IN' temp is over 137 degrees the CSD oil temp will exceed 157 degrees C. This is only one example . The other extreme is with a 'IN' temp of 157 degrees and a 'RISE' of 1 degree. I have been unable to get any confirmation of this as the boss won't bother Boeing for such a 'trivial' matter!