Mint Die Error

I recently purchased a lot of ten sequential NGC graded 2006 First Strikes graded Gem Uncirculated. While cherrypicking through them, I noticed all ten shared a similar blemish of two small parallel lines on the upper "stars" portion of the shield on the reverse. At first I thought these were bag marks, but they seem to be something that adhered to the die. I am interested if anyone else has this same die mark on their 2006 silver eagles, especially non first strike issues. Check yours and see.

eagle ches