The "proof photo" shows an old age Whitey Ford. This is Whitey well after Martin and Mantle had passed. So, unless someone can claim they had Martin and Mantle sign it, and then waited a decade or two before Whitey signed it... it doesn't hold up.
Here is my blog on that sham authenticator Guaranteed Forensics Authenticators (Stephen Rocchi) and the image you posted of those mass-produced forgeries out of Florida.