there is no way they authenticate every single signatures flow, pen pressue, slant, size, formation etc.
I would imagine they probably authenticate maybe the 10 most known autos and and if they pass assume the rest are authentic as well.
Also like DRC mentions, he probably had some documentation to go with some of the sigs as well and maybe he had many pictures of the different Negro Leaguers signing this piece. Like i already stated, i highly doubt each auto is authenticated personally.
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