Opinions on the authenticity of a Mantle autographed ball

[WallSparks]

I picked up a small box lot of vintage baseball from an estate sale (I know instant red flag, but I bought for the cards the ball was an extra) The cards all seem legit, no reason to think their not, there was nothing amazing in there, just some lower/average grade stars and HoFers from the early 60s and 70s.

This ball was in the box as well. It's a 1978 World Series ball. Sigs I can decipher are Mantle, Billy Martin and Graig Nettles. I know there are prob more fakes than real Mantle autos out there so here I am. Any chance this is legit or no.

I'm not even close to knowledgeable about vintage autos, I'm sure some of you may think it's a laughable fake but I have no clue. I usually use blowoutforums but I'm here for the experts!
What do you guys think?

Thanks,
Jeremy

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