Does Amazon have a number on the card to call for the balance, or is that only a thing with cards for brick and mortar shops?
For what it’s worth, if the gift card was purchased at a store, part of the back needs to be torn off for it to be scanned and activated, which makes all those cards look tampered with. Not sure if that’s what you’re seeing or not.
I've got a crazy bizarre idea. Why don't you contact Amazon customer service and ask them about it?
You can describe the cards and give them the numbers and then tell them why you believe they've been tampered.
I mean it's totally illogical, right?
When I was accused of possessing counterfeit money, I went right to my bank and showed the bills to them (they were, of course, authentic).
Create a new Amazon account just redeem them? TLDR Sacrificial account.
This will 100% never work, it is exactly the kind of thing Amazon etc will prevent. There is not a single business that accepts gift cards that will not immediately flag this and kill the account. It is the first thing you’d write if you were in charge of this, right?
Have you tried it?
Amazon ($25) and iCloud (this one was $10, bought from apple.com), both killed the account, did not try others but safe to assume results would be the same