I should start by saying that I collect mostly cartoon (US) animation art and not much anime (even though I love a lot of anime as well

Well... a couple months ago I happened upon what looked like a great item:

The description was sparse to say the least and the pictures left a lot to be desired. I was immediately concerned that the logo in the bottom right corner looked faded and the whole thing looked flat. I should have trusted my gut but I WANTED it to be real and the auction was just about to end. I did the stupid thing and made the impulse buy for what would have been a (fairly) reasonable price.
A few days later I get it in the mail. It's not a cel... it's not a drawing... it's not production art of any kind. It's an image that has been printed on foam board and then glued to a low quality mat:

Ugh. I immediately contact the seller and (very politely) explain that the item is not as described, that it was probably a mistake, that I'd be happy to send the item back (at my expense), I just want my money back. The seller sends a very short message back simply saying that the item is as described, is production art, and no refunds will be offered. Thus I am forced to open a case with eBay.
eBay is normally pretty good about this stuff. However, when claiming an item is counterfeit, it is up to the buyer to prove that it is. I wracked my brain on how I could do that. Pictures don't do a very good job of proving whether something is or isn't production art... especially to an eBay caseworker who probably doesn't know anything about animation art. Then it hits me! I remembered something I bought years ago on Kickstarter... something that I never thought would actually be useful... a small, rubber lens that turns your phone's camera into a 15x microscope. With it, I was able to take super-close-up photos of the item, showing the actual printer ink lines on the foam board:


I wrote a detailed explanation with the above images as well as examples of what production art and the WB seal should look like. I won my case in a matter of hours... all thanks to a $10 phone lens.

Moral of the story: Trust your gut.