That makes more sense. I was thinking it was from the die getting filled with dust or oil.

So we start out with Frosted because the die is newly cut, clean and perfect. As the die gets polished, it dulls the finish on the silver strike. If the die gets polished too much it can eliminate some of the detail on the strike as it is minted. Eventually, the die will have to be replaced because the detail gets removed by the polishing and the die no longer represents the original image.

Cool Beans - Thanks Walt. It is like I was just at the mint watching the strike making process.

I truly admire the artists who create the images that are originally on the die for minting. The attention to detail is amazing.