Featured is a Willie Mays signed first day cover. This cover has been hand signed by Mays and has been authenticated and encapsulated by Beckett. This cover would make a great addition to any sports memorabilia collection! Sign up for our Sports Integrity Newsletter for deals and upcoming autograph signings! Sign up to receive special insider notifications of deals and upcoming autograph signings!Willie Mays San Francisco Giants Signed Slabbed First Day Cover BAS. My about us text goes here. My authenticity guarantee text goes here.