To play devil's advocate...
Assuming that the JSA cert is indeed a fake...then the forger did a pretty good job on the letter itself.
Would someone take the time to produce a well made cert, then turn-around and try to pass off such a bad looking Ruth as legit? (And in my opinion, the auto is awful....if Ruth signed it, he must have done it with his off-hand).
And if this auto is actually certified...then I'm more confused than ever