I have this 2001 Silver proof set and have been wondering what this is since I received this set for my birthday back in 2001. I don't think it is doubling or missing clad but I have no idea what it would be. Above certain letters, most prominently on the word "States", it looks like some sort of silver or zinc lines that mirror the letters. I will greatly appreciate any sort of clarity on this subject. Thank you all so much.