It sounds like a piece with potential to be worth $10,000 or more if the signatures are genuine and in strong condition--collectors almost always pay a premium for "vintage" autographs, and a bat signed by Mantle and Maris during the "M&M Boys" days would be highly desirable. And, as someone noted, if it is a game used bat from a major star, the value could be even higher. Heritage is happy to provide free auction estimates at our website,
https://sports.ha.com/common/acquisi...Consign-071107, or you can email me directly with images of the bat. Heritage will also acquire the necessary authentication paperwork from both PSA/DNA and James Spence on your behalf, should you decide to consign to a Heritage auction.