Why is the finish so dull on UNC 1oz. Silver Eagles Dollars. Also,why is it that there seems to be a lot of variance on the dullness or brilliance of them. Most seem to have a "circle" of this variance about have way out to the total diameter. Other modern coins have "shinyness" to them, some looking prooflike, like uncirculated silver quarters and dimes. What makes the silver eagles so different? Just curious.........thanks