So you know how the ANA dealers have to accept a coin back if the customer finds it is a fake? What about counterfeit slabs? stainless
Any ANA dealer has a lifetime promise of authenticity, no time limit. Coins, slabs, paper, medals, anything, lifetime forever.
Picture archives Noost, always keep a pic file on every coin you ship. That is your only defense in case of a coin switcher, your word vs his. Hopefully a credibilty track record will count for something.
You can't, pictures prove nothing. All you have going for you is trust. You have to trust the dealer to sell you genuine coins - and he has to trust you not to switch coins out.
Dealers are supposed to follow a code of ethics when in the ANA. There are no guarantees the dealer is going to follow them, but they can be reported to the ANA if they violate any of these principles. I've learned to trust my local coin dealer very well. He also happens to be an ANA member, giving credit to the organization. I have since joined myself and do not regret it.