Mariano Rivera won the MVP of the 1999 World Series, and signed this Yankees team signed ball, along with the likes of Paul O'Neil, Andy Pettite, Roger Clemens, Derek Jeter, Bernie Williams, coaches Jose Cardenal and Don Zimmer, and manager Joe Torre, among the 19. Ball is Mint, and the signatures are 9s and 10s. Certificate of Authenticity (Steiner Authentic) enclosed.