Is the area that is marked covered by the scales ? If so I suspect some moisture was present regardless of how dry you think it was.
Originally Posted by Bruno
This is an extremely important point that bears repeating.
I have seen many razors which had been put away with some residual moisture or soap inside the scales, with spots or worse as the result.
+2 or 3
I don't ever even close the razor until the next day, it sits in a seperate drawer after all the wiping down etc: open until the next day, then it goes back in it's normal spot, and the next razor comes out to play