I believe this is one of the very common forgeries from the 1990s, but I'm not a Mantle expert, by any means.
I don't like the slant, the speed and the M's. But again, I'm not a Mantle expert. There are some guys on this site who've studied Mantle for decades.
I understand your concerns. I think the Mantle ball is likely real, but I wasn't confident enough to comment on it.
Oh yeah, that's a nice authentic Mantle ball.
Found some free time over the past few days and researched Mantle autographs. Yep; she's the real deal. You have a legit Mantle signature and I've had a chance to learn a few things. Thanks for posting!