This badge tells you that the seller permanently guarantees the item being sold to be original and accurately identified. Though the seller may have a return policy that restricts returns for other reasons to a certain specified time limit, an item that the buyer later finds not to be accurately identified or original may be returned to the seller at any time.
 
Specifically, this is what the seller has agreed to:

1) Be thorough, accurate, and careful when evaluating items before listing them for sale.

2) If a customer purchases an item and later asks to return it because the originality of the item is question, the seller will accept the return for a refund of the original purchase price regardless of the amout of time that has elapsed between the sale and the return.

3) If the seller does not have funds immediately available to cover an unexpected late return, special arrangements can be made, but the matter must be completely settled within 90 days of the return request.  If the buyer agrees to accept credit, trade merchandise, etc., that is fine - but a refund for the item's purchase price must always be an option open to the buyer.

4) If the buyer has cleaned, polished, 'repaired', modified, or altered the item, the seller is not obilgated to accept it for return. 

5)  Failure to honor the Guarantee may result in permanent loss of the seller's Weekly Militaria Show table, without a refund of the annual table fee.
 
What if the buyer is wrong, and the item is actually 100% correct?

The seller can certainly present the buyer with supporting documentation, other expert opinions, etc. in order to salvage the transaction.. but in the end if the buyer remains convinced that the item is not original and wishes to return it, the seller is obligated to accept the return. 
 
Buyer's Responsibilities: Dos and Don'ts

Don't abuse the system.  Make sure that when you contact a seller weeks, months, or longer after a sale to request a 'Guaranteed Original' refund, you are reasonably certain that the item truly is not original.

Do consult experts and specialists to make sure you are making the right decision.

Don't put too much faith in online forum opinions, one way or the other.  Some of the world's best specialists are indeed on the forums, but often the quickest 'experts' to respond with an authoritative opinion turn out to be guys whose experience is actually quite limited (or non-existent.)

Do exercise diplomacy.  For the most part, a seller who displays the Guaranteed Original logo is going to be one of the good guys who wants to be a responsible seller and a friend to his customers.  If you begin by publicly berating him on a collector's forum, or use hostile dialogue in your communications, chances are he will not see you as a friend that he needs to help.

Do be patient.  If you have had an item for the better part of a year and are just now finding that there is a problem, a few days or weeks shouldn't matter all that much.  Sometimes a return comes in at just the wrong time.  If your seller needs a few days or weeks to raise funds for your return, be gracious.  Remember - most sellers on the web do not accept late returns, whether they were incorrect or not.  Be glad your seller is one of the good guys, and work with him.
 
Disclaimer & Legal Stuff:

AGM Insider (owners, employees, and duly appointed agents thereof) are not in any way implying that we can or will accept any financial or legal responsibility for transactions initiated between members on this sales venue.  The Guarantee is solely between the seller and the buyer.  AGM Insider will not act as a referee in any disputes about whether an item is or is not original.  If an item was sold under the Guarantee and the seller fails to honor his obligations, the extent of AGM Insider's power is to freeze or terminate that individual's seller status, Insider membership, or both.