I recently picked up a white dialed Astro. From the pics I thought it was a silver dial one, but when it showed up, it turned out to be a white dial M9 type 1 US spec. My first thought was that it was a really bad redial, but then I looked closely at the font on the dial and saw that it matched my m5 black dial Astro, so likely not a redial. I did some more digging and found one other copy of a white dial but its an enhanced one, from 1968, so same time period as mine.
Clearly these are uncommon.