This is an Official M.L.B Baseball that has been hand signed by Ken Griffey Jr. & Ken Griffey Sr. This item was inscribed "Back To Back HR 9/4/90" by Ken Griffey Sr. This item has been witnessed and certified authentic by Beckett Authentication (BAS) and comes with their tamper-proof witness sticker. Beckett Authentication has recently changed their physical certificate card policy where they no longer match their tamper-proof sticker with a physical certificate. A certificate can be printed on Beckett's website for the matching authentication number. This item has also been certified authentic by TriStar and comes with their tamper-proof sticker and matching certificate of authenticity.