I have a "Bona-Fide" John Wigfall & Co., Sheffield razor in dark horn scales that has almost the same areas of rust as yours does. The spine area and parts of the blade that were not in the scales was almost black and lots of small pits. The edge area is fine..... I'll be sanding the heck out of mine to at least remove most of dark areas. I've made a ton of progress. The pits will be there, but I can live with it. I'm hoping mine will be a good shaver.... I think it will be.

On a newer blade like your.....very baffling to say the least. How old is your razor? I'm guessing fairly new.