Mickey Mantle Roger Maris Dual Signed BaseballA Mickey Mantle, Roger Maris Dual signed Baseball is worth about $3,000.-$5,000. Price will vary based on condition, type of authenticity that accompanies the signatures, and which signature is on the sweet spot. One player or the other on the sweet spot might not be worth more than the other, but if a collector bidding on the ball is a favorite of one or the other that collector will pay more for that player on the sweet spot.
In an October 2007 auction a Mickey Mantle, Roger Maris Dual signed baseball sold for $4,780.00 (Mantle on sweet spot). Signatures that have not been authenticated could sell at half the market value or less.