Looks a little shaky in spots which is a sign it is a forgery. Also the “COA” states that many of these were “signed” which indicates the seller had a bunch of these for sale. Usually a red flag when someone is selling multiples of a valuable autograph.
I am no expert on this, but if I saw that "certificate" I would walk away. Using "grandmother" and then going into a fairly deep explanation of things (he was very generous and he signed many-he's a fast writer and so kind" is a bit too blah blah blah for a legit seller. If it's legit, it's legit and you don't need some faksih provenance poorly copied onto a crookedly cut piece of junk paper to prove it. My thoughts.