[WallaceRoger]

I have this exact issue with mine. I'm more bothered by the warp than the grime (I can clean grime slowly with a magnifier and tiny brush).

Mcusi, the dial itself is attached with rivets, so you could probably just drill out the existing rivets to remove the old one, then attach the new one with pop rivets or small sheet metal screws.

I can't tell if the warp in mine is due to the metal expanding/contracting over time, or if it's due to heat. I may drill out one of my rivets to see if releasing some of the tension allows it to pop back into form. If not, may try softening with a heat gun and pressing back into place.