The info on that page is completely incorrect
"Each of these 2015 American Silver Eagle coins originated at the Philadelphia Mint. Although bullion coins bear no mint marks, the origin at the Philadelphia Mint is established by the coins arriving for certification in a sealed US Mint box featuring 6-digit serial numbers starting with the number 5."

Here is the FOIA request info:
http://www.silverdoctors.com/silver/silver-coins/us-mint-forced-to-reveal-79640-silver-eagles-struck-at-philadelphia-mint-in-2015/
2015 is 5 digit number starting with 1, not 6 digit numbers starting with 5 (that was 2016 & 2017)