For vintage cards I would go with PSA or SGC. Personally, I no longer consider GAI to be reputable and have not for a long time (though they were when they started). That is only my opinion, but you can easily see it reflected in the prices GAI graded cards get. I would imagine most cards in their holders are authentic, but you would probably find that many are over-graded or altered if you tried to cross them to PSA or SGC. That is not to say there aren't perfectly legit, unaltered cards still in their holders. It is just that the numbers are dwindling.
JimB
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