That sure is odd, couln't tell what that is. Just to give you a heads up, I have had excellent results storing ASE's in vacuum sealed bags. Some have been sealed for 6 years, no milk, no spots. I use the Food Saver brand. Good luck with your Eagle's.
I recently sent in 14 of my 18 20th Ann American Silver eagles for milk spot review PCGS ended up giving me money... Now I only have one complete 20th ann silver set I hvae since taken the advise of morgansforever and vacume packed all of my coins.