2007-D Idaho quarter - strange field texture

On the right - a regular quarter with unc details. On the left - super shiny BU, but what's going on with the background texture? Plated? Color doesn't look like silver. Satin finish? 

odd It may be what i have heard called orange peel. It an error from the die is on its last legs.  Makes the surface of the coin look like an orange peel. Or something wrong with the pressure on the press. To high of pressure can cause waves. Iam not sure , hope more people gave their thoughts.