It's funny that this question can now be earnestly asked, incl. by PSA fans
 

Which company is/was more reliable at identifying altered cards: PSA or GAI?

Early GAI, or late, "we'll do anything for a buck" GAI?

Even better question:

Which company is more reliable at identifying altered cards: PSA or KSA? :D

Has to be BOD

Good question.

You are more likely to get a trimmed card by buying it in a PSA slab than buying it raw.

I truly believe it depends upon who is submitting the cards. I think the grading standard differs for “preferred” customers.

You’re not likely to get many honest answers here. Too many people who want to protect their investments, choose to look past the corruption, and want to maintain the status quo.

Since nobody has really answered the OP’s question about detecting alteration, I’ll give my 2 cents...

1. Advanced collectors’ own sets of eyes
2. SGC
3. Original GAI
4. PSA

In your list would Magic 8 ball rank 4 or 5? :D

It depends on the 8 Ball...

If manufactured in the 1960s, I would rank it #4. If made in the 1970s and beyond, I’d rank it behind PSA. Mattel’s quality control began to diminish after their initial run. That’s about when the Ouija Board became the preferred technology, thus surpassing the Magic 8 Ball.

So the full ranking is as follows...

1. Our own eyes
2. SGC
3. Early Global
4. ‘60s Magic 8 Ball
5. Ouija Board
6. PSA
7. ‘70s Magic 8 Ball
8. Late Global

In defense of PSA, Pro would rank 17, and AAA wouldn't qualify because nothing they graded qualified a card.

The real funny thing is BCCC might be #1.

BCCC, heh, their 'whatever' grade just cracks me up. I have one card:

https://photos.imageevent.com/exhibi...20Mays%201.jpg

Only reason it is still slabbed is that the Beckett slabs are hard to open.

We also forgot original (red label) SCD:

https://photos.imageevent.com/exhibi...ps%20Spahn.jpg

I thought they did a good job and had a nice holder, but the venture fizzled and they sold to some clown who rebranded with blue labels and turned it into a PRO.

Also a fond shout out to CSA: remember that one? I got some great cards in CSA holders but also some clunkers. Those bright blue holders were...interesting.

An experienced eye, hobby knowledge, logic, common sense and the input of friends make up something currently more reliable at identifying altered raw cards than a PSA label. If one needs evidence, mere common sense points to most high-grade Pre-War cards in PSA holders likely being altered. Yet PSA has labeled them all as unaltered.

Granted, PSA is the particular target of sneaky altered cards (though much of their own making--formation of PSA registry, marketing, apparently allowing known alterers to continue to submit cards, etc.), but that's a reason (or excuse for) why the facts are the facts not a refutation of the facts.