This Autographed Game Used White Russell Athletic Home Size 48 +1 Sleeve Length Jersey with the inscription of "To Shaq, The Best To You On A Hall Of Fame Career" has been Personally Signed by Mark McGwire of the Oakland Athletics. This item is 100% Authentic to include a Certificate of Authenticity (COA) / hologram by Beckett Authentication Services. The authenticity can be verified on Beckett Authentication Services website. The jersey also comes with a letter of authenticity from Sports Investors Authentication for the game use along with a letter of authenticity from Shaquille O'Neal for the provenance as well.